docs: organize the specification
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Zach Ramsay
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Minimal makefile for Sphinx documentation
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# Minimal makefile for Sphinx documentation
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#
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# You can set these variables from the command line.
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Block Structure
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===============
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The tendermint consensus engine records all agreements by a
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supermajority of nodes into a blockchain, which is replicated among all
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nodes. This blockchain is accessible via various rpc endpoints, mainly
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``/block?height=`` to get the full block, as well as
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``/blockchain?minHeight=_&maxHeight=_`` to get a list of headers. But
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what exactly is stored in these blocks?
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Block
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~~~~~
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A
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`Block <https://godoc.org/github.com/tendermint/tendermint/types#Block>`__
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contains:
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- a `Header <#header>`__ contains merkle hashes for various chain
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states
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- the
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`Data <https://godoc.org/github.com/tendermint/tendermint/types#Data>`__
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is all transactions which are to be processed
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- the `LastCommit <#commit>`__ > 2/3 signatures for the last block
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The signatures returned along with block ``H`` are those validating
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block ``H-1``. This can be a little confusing, but we must also consider
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that the ``Header`` also contains the ``LastCommitHash``. It would be
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impossible for a Header to include the commits that sign it, as it would
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cause an infinite loop here. But when we get block ``H``, we find
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``Header.LastCommitHash``, which must match the hash of ``LastCommit``.
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Header
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~~~~~~
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The
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`Header <https://godoc.org/github.com/tendermint/tendermint/types#Header>`__
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contains lots of information (follow link for up-to-date info). Notably,
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it maintains the ``Height``, the ``LastBlockID`` (to make it a chain),
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and hashes of the data, the app state, and the validator set. This is
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important as the only item that is signed by the validators is the
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``Header``, and all other data must be validated against one of the
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merkle hashes in the ``Header``.
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The ``DataHash`` can provide a nice check on the
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`Data <https://godoc.org/github.com/tendermint/tendermint/types#Data>`__
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returned in this same block. If you are subscribed to new blocks, via
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tendermint RPC, in order to display or process the new transactions you
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should at least validate that the ``DataHash`` is valid. If it is
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important to verify autheniticity, you must wait for the ``LastCommit``
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from the next block to make sure the block header (including
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``DataHash``) was properly signed.
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The ``ValidatorHash`` contains a hash of the current
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`Validators <https://godoc.org/github.com/tendermint/tendermint/types#Validator>`__.
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Tracking all changes in the validator set is complex, but a client can
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quickly compare this hash with the `hash of the currently known
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validators <https://godoc.org/github.com/tendermint/tendermint/types#ValidatorSet.Hash>`__
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to see if there have been changes.
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The ``AppHash`` serves as the basis for validating any merkle proofs
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that come from the `ABCI
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application <https://github.com/tendermint/abci>`__. It represents the
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state of the actual application, rather that the state of the blockchain
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itself. This means it's necessary in order to perform any business
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logic, such as verifying and account balance.
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**Note** After the transactions are committed to a block, they still
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need to be processed in a separate step, which happens between the
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blocks. If you find a given transaction in the block at height ``H``,
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the effects of running that transaction will be first visible in the
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``AppHash`` from the block header at height ``H+1``.
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Like the ``LastCommit`` issue, this is a requirement of the immutability
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of the block chain, as the application only applies transactions *after*
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they are commited to the chain.
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Commit
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~~~~~~
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The
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`Commit <https://godoc.org/github.com/tendermint/tendermint/types#Commit>`__
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contains a set of
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`Votes <https://godoc.org/github.com/tendermint/tendermint/types#Vote>`__
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that were made by the validator set to reach consensus on this block.
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This is the key to the security in any PoS system, and actually no data
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that cannot be traced back to a block header with a valid set of Votes
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can be trusted. Thus, getting the Commit data and verifying the votes is
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extremely important.
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As mentioned above, in order to find the ``precommit votes`` for block
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header ``H``, we need to query block ``H+1``. Then we need to check the
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votes, make sure they really are for that block, and properly formatted.
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Much of this code is implemented in Go in the
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`light-client <https://github.com/tendermint/light-client>`__ package.
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If you look at the code, you will notice that we need to provide the
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``chainID`` of the blockchain in order to properly calculate the votes.
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This is to protect anyone from swapping votes between chains to fake (or
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frame) a validator. Also note that this ``chainID`` is in the
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``genesis.json`` from *Tendermint*, not the ``genesis.json`` from the
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basecoin app (`that is a different
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chainID... <https://github.com/tendermint/basecoin/issues/32>`__).
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Once we have those votes, and we calculated the proper `sign
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bytes <https://godoc.org/github.com/tendermint/tendermint/types#Vote.WriteSignBytes>`__
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using the chainID and a `nice helper
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function <https://godoc.org/github.com/tendermint/tendermint/types#SignBytes>`__,
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we can verify them. The light client is responsible for maintaining a
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set of validators that we trust. Each vote only stores the validators
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``Address``, as well as the ``Signature``. Assuming we have a local copy
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of the trusted validator set, we can look up the ``Public Key`` of the
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validator given its ``Address``, then verify that the ``Signature``
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matches the ``SignBytes`` and ``Public Key``. Then we sum up the total
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voting power of all validators, whose votes fulfilled all these
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stringent requirements. If the total number of voting power for a single
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block is greater than 2/3 of all voting power, then we can finally trust
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the block header, the AppHash, and the proof we got from the ABCI
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application.
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Vote Sign Bytes
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^^^^^^^^^^^^^^^
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The ``sign-bytes`` of a vote is produced by taking a
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```stable-json`` <https://github.com/substack/json-stable-stringify>`__-like
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deterministic JSON ```wire`` </docs/specs/wire-protocol>`__ encoding of
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the vote (excluding the ``Signature`` field), and wrapping it with
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``{"chain_id":"my_chain","vote":...}``.
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For example, a precommit vote might have the following ``sign-bytes``:
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.. code:: json
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{"chain_id":"my_chain","vote":{"block_hash":"611801F57B4CE378DF1A3FFF1216656E89209A99","block_parts_header":{"hash":"B46697379DBE0774CC2C3B656083F07CA7E0F9CE","total":123},"height":1234,"round":1,"type":2}}
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Block Hash
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~~~~~~~~~~
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The `block
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hash <https://godoc.org/github.com/tendermint/tendermint/types#Block.Hash>`__
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is the `Simple Tree hash <Merkle-Trees#simple-tree-with-dictionaries>`__
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of the fields of the block ``Header`` encoded as a list of
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``KVPair``\ s.
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Transaction
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~~~~~~~~~~~
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A transaction is any sequence of bytes. It is up to your
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`ABCI <https://github.com/tendermint/abci>`__ application to accept or
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reject transactions.
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BlockID
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~~~~~~~
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Many of these data structures refer to the
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`BlockID <https://godoc.org/github.com/tendermint/tendermint/types#BlockID>`__,
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which is the ``BlockHash`` (hash of the block header, also referred to
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by the next block) along with the ``PartSetHeader``. The
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``PartSetHeader`` is explained below and is used internally to
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orchestrate the p2p propogation. For clients, it is basically opaque
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bytes, but they must match for all votes.
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PartSetHeader
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~~~~~~~~~~~~~
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The
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`PartSetHeader <https://godoc.org/github.com/tendermint/tendermint/types#PartSetHeader>`__
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contains the total number of pieces in a
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`PartSet <https://godoc.org/github.com/tendermint/tendermint/types#PartSet>`__,
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and the Merkle root hash of those pieces.
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PartSet
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~~~~~~~
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PartSet is used to split a byteslice of data into parts (pieces) for
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transmission. By splitting data into smaller parts and computing a
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Merkle root hash on the list, you can verify that a part is legitimately
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part of the complete data, and the part can be forwarded to other peers
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before all the parts are known. In short, it's a fast way to securely
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propagate a large chunk of data (like a block) over a gossip network.
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PartSet was inspired by the LibSwift project.
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Usage:
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.. code:: go
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data := RandBytes(2 << 20) // Something large
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partSet := NewPartSetFromData(data)
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partSet.Total() // Total number of 4KB parts
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partSet.Count() // Equal to the Total, since we already have all the parts
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partSet.Hash() // The Merkle root hash
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partSet.BitArray() // A BitArray of partSet.Total() 1's
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header := partSet.Header() // Send this to the peer
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header.Total // Total number of parts
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header.Hash // The merkle root hash
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// Now we'll reconstruct the data from the parts
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partSet2 := NewPartSetFromHeader(header)
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partSet2.Total() // Same total as partSet.Total()
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partSet2.Count() // Zero, since this PartSet doesn't have any parts yet.
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partSet2.Hash() // Same hash as in partSet.Hash()
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partSet2.BitArray() // A BitArray of partSet.Total() 0's
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// In a gossip network the parts would arrive in arbitrary order, perhaps
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// in response to explicit requests for parts, or optimistically in response
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// to the receiving peer's partSet.BitArray().
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for !partSet2.IsComplete() {
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part := receivePartFromGossipNetwork()
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added, err := partSet2.AddPart(part)
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if err != nil {
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// A wrong part,
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// the merkle trail does not hash to partSet2.Hash()
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} else if !added {
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// A duplicate part already received
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}
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}
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data2, _ := ioutil.ReadAll(partSet2.GetReader())
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bytes.Equal(data, data2) // true
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@ -0,0 +1,352 @@
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Byzantine Consensus Algorithm
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=============================
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*The draft 0.6 whitepaper is outdated. The new algorithm is detailed
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below. See `revisions <#revisions>`__*
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Terms
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-----
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- The network is composed of optionally connected *nodes*. Nodes
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directly connected to a particular node are called *peers*.
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- The consensus process in deciding the next block (at some *height*
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``H``) is composed of one or many *rounds*.
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- ``NewHeight``, ``Propose``, ``Prevote``, ``Precommit``, and
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``Commit`` represent state machine states of a round. (aka
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``RoundStep`` or just "step").
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- A node is said to be *at* a given height, round, and step, or at
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``(H,R,S)``, or at ``(H,R)`` in short to omit the step.
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- To *prevote* or *precommit* something means to broadcast a `prevote
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vote <https://godoc.org/github.com/tendermint/tendermint/types#Vote>`__
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or `first precommit
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vote <https://godoc.org/github.com/tendermint/tendermint/types#FirstPrecommit>`__
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for something.
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- A vote *at* ``(H,R)`` is a vote signed with the bytes for ``H`` and
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``R`` included in its
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```sign-bytes`` </docs/specs/block-structure#vote-sign-bytes>`__.
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- *+2/3* is short for "more than 2/3"
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- *1/3+* is short for "1/3 or more"
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- A set of +2/3 of prevotes for a particular block or ``<nil>`` at
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``(H,R)`` is called a *proof-of-lock-change* or *PoLC* for short.
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State Machine Overview
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----------------------
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At each height of the blockchain a round-based protocol is run to
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determine the next block. Each round is composed of three *steps*
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(``Propose``, ``Prevote``, and ``Precommit``), along with two special
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steps ``Commit`` and ``NewHeight``.
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In the optimal scenario, the order of steps is:
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::
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NewHeight -> (Propose -> Prevote -> Precommit)+ -> Commit -> NewHeight ->...
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The sequence ``(Propose -> Prevote -> Precommit)`` is called a *round*.
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There may be more than one round required to commit a block at a given
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height. Examples for why more rounds may be required include:
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- The designated proposer was not online.
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- The block proposed by the designated proposer was not valid.
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- The block proposed by the designated proposer did not propagate in
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time.
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- The block proposed was valid, but +2/3 of prevotes for the proposed
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block were not received in time for enough validator nodes by the
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time they reached the ``Precommit`` step. Even though +2/3 of
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prevotes are necessary to progress to the next step, at least one
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validator may have voted ``<nil>`` or maliciously voted for something
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else.
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- The block proposed was valid, and +2/3 of prevotes were received for
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enough nodes, but +2/3 of precommits for the proposed block were not
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received for enough validator nodes.
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Some of these problems are resolved by moving onto the next round &
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proposer. Others are resolved by increasing certain round timeout
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parameters over each successive round.
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State Machine Diagram
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---------------------
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::
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+-------------------------------------+
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v |(Wait til `CommmitTime+timeoutCommit`)
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+-----------+ +-----+-----+
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+----------> | Propose +--------------+ | NewHeight |
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| +-----------+ | +-----------+
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| | ^
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|(Else, after timeoutPrecommit) v |
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+-----+-----+ +-----------+ |
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| Precommit | <------------------------+ Prevote | |
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+-----+-----+ +-----------+ |
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|(When +2/3 Precommits for block found) |
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v |
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+--------------------------------------------------------------------+
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| Commit |
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| |
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| * Set CommitTime = now; |
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| * Wait for block, then stage/save/commit block; |
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+--------------------------------------------------------------------+
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Background Gossip
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-----------------
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A node may not have a corresponding validator private key, but it
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nevertheless plays an active role in the consensus process by relaying
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relevant meta-data, proposals, blocks, and votes to its peers. A node
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that has the private keys of an active validator and is engaged in
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signing votes is called a *validator-node*. All nodes (not just
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validator-nodes) have an associated state (the current height, round,
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and step) and work to make progress.
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Between two nodes there exists a ``Connection``, and multiplexed on top
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of this connection are fairly throttled ``Channel``\ s of information.
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An epidemic gossip protocol is implemented among some of these channels
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to bring peers up to speed on the most recent state of consensus. For
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example,
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- Nodes gossip ``PartSet`` parts of the current round's proposer's
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proposed block. A LibSwift inspired algorithm is used to quickly
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broadcast blocks across the gossip network.
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- Nodes gossip prevote/precommit votes. A node NODE\_A that is ahead of
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NODE\_B can send NODE\_B prevotes or precommits for NODE\_B's current
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(or future) round to enable it to progress forward.
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- Nodes gossip prevotes for the proposed PoLC (proof-of-lock-change)
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round if one is proposed.
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- Nodes gossip to nodes lagging in blockchain height with block
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`commits <https://godoc.org/github.com/tendermint/tendermint/types#Commit>`__
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for older blocks.
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- Nodes opportunistically gossip ``HasVote`` messages to hint peers
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what votes it already has.
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- Nodes broadcast their current state to all neighboring peers. (but is
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not gossiped further)
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There's more, but let's not get ahead of ourselves here.
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Proposals
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---------
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A proposal is signed and published by the designated proposer at each
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round. The proposer is chosen by a deterministic and non-choking round
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robin selection algorithm that selects proposers in proportion to their
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voting power. (see
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`implementation <https://github.com/tendermint/tendermint/blob/develop/types/validator_set.go>`__)
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A proposal at ``(H,R)`` is composed of a block and an optional latest
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``PoLC-Round < R`` which is included iff the proposer knows of one. This
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hints the network to allow nodes to unlock (when safe) to ensure the
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liveness property.
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State Machine Spec
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------------------
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Propose Step (height:H,round:R)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Upon entering ``Propose``: - The designated proposer proposes a block at
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``(H,R)``.
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The ``Propose`` step ends: - After ``timeoutProposeR`` after entering
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``Propose``. --> goto ``Prevote(H,R)`` - After receiving proposal block
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and all prevotes at ``PoLC-Round``. --> goto ``Prevote(H,R)`` - After
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`common exit conditions <#common-exit-conditions>`__
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Prevote Step (height:H,round:R)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Upon entering ``Prevote``, each validator broadcasts its prevote vote.
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- First, if the validator is locked on a block since ``LastLockRound``
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but now has a PoLC for something else at round ``PoLC-Round`` where
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``LastLockRound < PoLC-Round < R``, then it unlocks.
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- If the validator is still locked on a block, it prevotes that.
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- Else, if the proposed block from ``Propose(H,R)`` is good, it
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prevotes that.
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- Else, if the proposal is invalid or wasn't received on time, it
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prevotes ``<nil>``.
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The ``Prevote`` step ends: - After +2/3 prevotes for a particular block
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or ``<nil>``. --> goto ``Precommit(H,R)`` - After ``timeoutPrevote``
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after receiving any +2/3 prevotes. --> goto ``Precommit(H,R)`` - After
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`common exit conditions <#common-exit-conditions>`__
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Precommit Step (height:H,round:R)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Upon entering ``Precommit``, each validator broadcasts its precommit
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vote. - If the validator has a PoLC at ``(H,R)`` for a particular block
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``B``, it (re)locks (or changes lock to) and precommits ``B`` and sets
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``LastLockRound = R``. - Else, if the validator has a PoLC at ``(H,R)``
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for ``<nil>``, it unlocks and precommits ``<nil>``. - Else, it keeps the
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lock unchanged and precommits ``<nil>``.
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A precommit for ``<nil>`` means "I didn’t see a PoLC for this round, but
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I did get +2/3 prevotes and waited a bit".
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The Precommit step ends: - After +2/3 precommits for ``<nil>``. --> goto
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``Propose(H,R+1)`` - After ``timeoutPrecommit`` after receiving any +2/3
|
||||
precommits. --> goto ``Propose(H,R+1)`` - After `common exit
|
||||
conditions <#common-exit-conditions>`__
|
||||
|
||||
common exit conditions
|
||||
^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
- After +2/3 precommits for a particular block. --> goto ``Commit(H)``
|
||||
- After any +2/3 prevotes received at ``(H,R+x)``. --> goto
|
||||
``Prevote(H,R+x)``
|
||||
- After any +2/3 precommits received at ``(H,R+x)``. --> goto
|
||||
``Precommit(H,R+x)``
|
||||
|
||||
Commit Step (height:H)
|
||||
~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- Set ``CommitTime = now()``
|
||||
- Wait until block is received. --> goto ``NewHeight(H+1)``
|
||||
|
||||
NewHeight Step (height:H)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- Move ``Precommits`` to ``LastCommit`` and increment height.
|
||||
- Set ``StartTime = CommitTime+timeoutCommit``
|
||||
- Wait until ``StartTime`` to receive straggler commits. --> goto
|
||||
``Propose(H,0)``
|
||||
|
||||
Proofs
|
||||
------
|
||||
|
||||
Proof of Safety
|
||||
~~~~~~~~~~~~~~~
|
||||
|
||||
Assume that at most -1/3 of the voting power of validators is byzantine.
|
||||
If a validator commits block ``B`` at round ``R``, it's because it saw
|
||||
+2/3 of precommits at round ``R``. This implies that 1/3+ of honest
|
||||
nodes are still locked at round ``R' > R``. These locked validators will
|
||||
remain locked until they see a PoLC at ``R' > R``, but this won't happen
|
||||
because 1/3+ are locked and honest, so at most -2/3 are available to
|
||||
vote for anything other than ``B``.
|
||||
|
||||
Proof of Liveness
|
||||
~~~~~~~~~~~~~~~~~
|
||||
|
||||
If 1/3+ honest validators are locked on two different blocks from
|
||||
different rounds, a proposers' ``PoLC-Round`` will eventually cause
|
||||
nodes locked from the earlier round to unlock. Eventually, the
|
||||
designated proposer will be one that is aware of a PoLC at the later
|
||||
round. Also, ``timeoutProposalR`` increments with round ``R``, while the
|
||||
size of a proposal are capped, so eventually the network is able to
|
||||
"fully gossip" the whole proposal (e.g. the block & PoLC).
|
||||
|
||||
Proof of Fork Accountability
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Define the JSet (justification-vote-set) at height ``H`` of a validator
|
||||
``V1`` to be all the votes signed by the validator at ``H`` along with
|
||||
justification PoLC prevotes for each lock change. For example, if ``V1``
|
||||
signed the following precommits: ``Precommit(B1 @ round 0)``,
|
||||
``Precommit(<nil> @ round 1)``, ``Precommit(B2 @ round 4)`` (note that
|
||||
no precommits were signed for rounds 2 and 3, and that's ok),
|
||||
``Precommit(B1 @ round 0)`` must be justified by a PoLC at round 0, and
|
||||
``Precommit(B2 @ round 4)`` must be justified by a PoLC at round 4; but
|
||||
the precommit for ``<nil>`` at round 1 is not a lock-change by
|
||||
definition so the JSet for ``V1`` need not include any prevotes at round
|
||||
1, 2, or 3 (unless ``V1`` happened to have prevoted for those rounds).
|
||||
|
||||
Further, define the JSet at height ``H`` of a set of validators ``VSet``
|
||||
to be the union of the JSets for each validator in ``VSet``. For a given
|
||||
commit by honest validators at round ``R`` for block ``B`` we can
|
||||
construct a JSet to justify the commit for ``B`` at ``R``. We say that a
|
||||
JSet *justifies* a commit at ``(H,R)`` if all the committers (validators
|
||||
in the commit-set) are each justified in the JSet with no duplicitous
|
||||
vote signatures (by the committers).
|
||||
|
||||
- **Lemma**: When a fork is detected by the existence of two
|
||||
conflicting `commits </docs/specs/validators#commiting-a-block>`__,
|
||||
the union of the JSets for both commits (if they can be compiled)
|
||||
must include double-signing by at least 1/3+ of the validator set.
|
||||
**Proof**: The commit cannot be at the same round, because that would
|
||||
immediately imply double-signing by 1/3+. Take the union of the JSets
|
||||
of both commits. If there is no double-signing by at least 1/3+ of
|
||||
the validator set in the union, then no honest validator could have
|
||||
precommitted any different block after the first commit. Yet, +2/3
|
||||
did. Reductio ad absurdum.
|
||||
|
||||
As a corollary, when there is a fork, an external process can determine
|
||||
the blame by requiring each validator to justify all of its round votes.
|
||||
Either we will find 1/3+ who cannot justify at least one of their votes,
|
||||
and/or, we will find 1/3+ who had double-signed.
|
||||
|
||||
Alternative algorithm
|
||||
~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Alternatively, we can take the JSet of a commit to be the "full commit".
|
||||
That is, if light clients and validators do not consider a block to be
|
||||
committed unless the JSet of the commit is also known, then we get the
|
||||
desirable property that if there ever is a fork (e.g. there are two
|
||||
conflicting "full commits"), then 1/3+ of the validators are immediately
|
||||
punishable for double-signing.
|
||||
|
||||
There are many ways to ensure that the gossip network efficiently share
|
||||
the JSet of a commit. One solution is to add a new message type that
|
||||
tells peers that this node has (or does not have) a +2/3 majority for B
|
||||
(or ) at (H,R), and a bitarray of which votes contributed towards that
|
||||
majority. Peers can react by responding with appropriate votes.
|
||||
|
||||
We will implement such an algorithm for the next iteration of the
|
||||
Tendermint consensus protocol.
|
||||
|
||||
Other potential improvements include adding more data in votes such as
|
||||
the last known PoLC round that caused a lock change, and the last voted
|
||||
round/step (or, we may require that validators not skip any votes). This
|
||||
may make JSet verification/gossip logic easier to implement.
|
||||
|
||||
Censorship Attacks
|
||||
~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Due to the definition of a block
|
||||
`commit </docs/specs/validators#commiting-a-block>`__, any 1/3+
|
||||
coalition of validators can halt the blockchain by not broadcasting
|
||||
their votes. Such a coalition can also censor particular transactions by
|
||||
rejecting blocks that include these transactions, though this would
|
||||
result in a significant proportion of block proposals to be rejected,
|
||||
which would slow down the rate of block commits of the blockchain,
|
||||
reducing its utility and value. The malicious coalition might also
|
||||
broadcast votes in a trickle so as to grind blockchain block commits to
|
||||
a near halt, or engage in any combination of these attacks.
|
||||
|
||||
If a global active adversary were also involved, it can partition the
|
||||
network in such a way that it may appear that the wrong subset of
|
||||
validators were responsible for the slowdown. This is not just a
|
||||
limitation of Tendermint, but rather a limitation of all consensus
|
||||
protocols whose network is potentially controlled by an active
|
||||
adversary.
|
||||
|
||||
Overcoming Forks and Censorship Attacks
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
For these types of attacks, a subset of the validators through external
|
||||
means should coordinate to sign a reorg-proposal that chooses a fork
|
||||
(and any evidence thereof) and the initial subset of validators with
|
||||
their signatures. Validators who sign such a reorg-proposal forego its
|
||||
collateral on all other forks. Clients should verify the signatures on
|
||||
the reorg-proposal, verify any evidence, and make a judgement or prompt
|
||||
the end-user for a decision. For example, a phone wallet app may prompt
|
||||
the user with a security warning, while a refrigerator may accept any
|
||||
reorg-proposal signed by +½ of the original validators.
|
||||
|
||||
No non-synchronous Byzantine fault-tolerant algorithm can come to
|
||||
consensus when ⅓+ of validators are dishonest, yet a fork assumes that
|
||||
⅓+ of validators have already been dishonest by double-signing or
|
||||
lock-changing without justification. So, signing the reorg-proposal is a
|
||||
coordination problem that cannot be solved by any non-synchronous
|
||||
protocol (i.e. automatically, and without making assumptions about the
|
||||
reliability of the underlying network). It must be provided by means
|
||||
external to the weakly-synchronous Tendermint consensus algorithm. For
|
||||
now, we leave the problem of reorg-proposal coordination to human
|
||||
coordination via internet media. Validators must take care to ensure
|
||||
that there are no significant network partitions, to avoid situations
|
||||
where two conflicting reorg-proposals are signed.
|
||||
|
||||
Assuming that the external coordination medium and protocol is robust,
|
||||
it follows that forks are less of a concern than `censorship
|
||||
attacks <#censorship-attacks>`__.
|
||||
|
|
@ -0,0 +1,55 @@
|
|||
Configuration
|
||||
=============
|
||||
|
||||
TendermintCore can be configured via a TOML file in
|
||||
``$TMHOME/config.toml``. Some of these parameters can be overridden by
|
||||
command-line flags.
|
||||
|
||||
Config parameters
|
||||
~~~~~~~~~~~~~~~~~
|
||||
|
||||
The main config parameters are defined
|
||||
`here <https://github.com/tendermint/tendermint/blob/master/config/config.go>`__.
|
||||
|
||||
- ``abci``: ABCI transport (socket \| grpc). *Default*: ``socket``
|
||||
- ``db_backend``: Database backend for the blockchain and
|
||||
TendermintCore state. ``leveldb`` or ``memdb``. *Default*:
|
||||
``"leveldb"``
|
||||
- ``db_dir``: Database dir. *Default*: ``"$TMHOME/data"``
|
||||
- ``fast_sync``: Whether to sync faster from the block pool. *Default*:
|
||||
``true``
|
||||
- ``genesis_file``: The location of the genesis file. *Default*:
|
||||
``"$TMHOME/genesis.json"``
|
||||
- ``log_level``: *Default*: ``"state:info,*:error"``
|
||||
- ``moniker``: Name of this node. *Default*: ``"anonymous"``
|
||||
- ``priv_validator_file``: Validator private key file. *Default*:
|
||||
``"$TMHOME/priv_validator.json"``
|
||||
- ``prof_laddr``: Profile listen address. *Default*: ``""``
|
||||
- ``proxy_app``: The ABCI app endpoint. *Default*:
|
||||
``"tcp://127.0.0.1:46658"``
|
||||
|
||||
- ``consensus.max_block_size_txs``: Maximum number of block txs.
|
||||
*Default*: ``10000``
|
||||
- ``consensus.timeout_*``: Various consensus timeout parameters
|
||||
**TODO**
|
||||
- ``consensus.wal_file``: Consensus state WAL. *Default*:
|
||||
``"$TMHOME/data/cswal"``
|
||||
- ``consensus.wal_light``: Whether to use light-mode for Consensus
|
||||
state WAL. *Default*: ``false``
|
||||
|
||||
- ``mempool.*``: Various mempool parameters **TODO**
|
||||
|
||||
- ``p2p.addr_book_file``: Peer address book. *Default*:
|
||||
``"$TMHOME/addrbook.json"``. **NOT USED**
|
||||
- ``p2p.laddr``: Node listen address. (0.0.0.0:0 means any interface,
|
||||
any port). *Default*: ``"0.0.0.0:46656"``
|
||||
- ``p2p.pex``: Enable Peer-Exchange (dev feature). *Default*: ``false``
|
||||
- ``p2p.seeds``: Comma delimited host:port seed nodes. *Default*:
|
||||
``""``
|
||||
- ``p2p.skip_upnp``: Skip UPNP detection. *Default*: ``false``
|
||||
|
||||
- ``rpc.grpc_laddr``: GRPC listen address (BroadcastTx only). Port
|
||||
required. *Default*: ``""``
|
||||
- ``rpc.laddr``: RPC listen address. Port required. *Default*:
|
||||
``"0.0.0.0:46657"``
|
||||
- ``rpc.unsafe``: Enabled unsafe rpc methods. *Default*: ``true``
|
||||
|
|
@ -0,0 +1,34 @@
|
|||
Fast Sync
|
||||
=========
|
||||
|
||||
Background
|
||||
----------
|
||||
|
||||
In a proof of work blockchain, syncing with the chain is the same
|
||||
process as staying up-to-date with the consensus: download blocks, and
|
||||
look for the one with the most total work. In proof-of-stake, the
|
||||
consensus process is more complex, as it involves rounds of
|
||||
communication between the nodes to determine what block should be
|
||||
committed next. Using this process to sync up with the blockchain from
|
||||
scratch can take a very long time. It's much faster to just download
|
||||
blocks and check the merkle tree of validators than to run the real-time
|
||||
consensus gossip protocol.
|
||||
|
||||
Fast Sync
|
||||
---------
|
||||
|
||||
To support faster syncing, tendermint offers a ``fast-sync`` mode, which
|
||||
is enabled by default, and can be toggled in the ``config.toml`` or via
|
||||
``--fast_sync=false``.
|
||||
|
||||
In this mode, the tendermint daemon will sync hundreds of times faster
|
||||
than if it used the real-time consensus process. Once caught up, the
|
||||
daemon will switch out of fast sync and into the normal consensus mode.
|
||||
After running for some time, the node is considered ``caught up`` if it
|
||||
has at least one peer and it's height is at least as high as the max
|
||||
reported peer height. See `the IsCaughtUp
|
||||
method <https://github.com/tendermint/tendermint/blob/b467515719e686e4678e6da4e102f32a491b85a0/blockchain/pool.go#L128>`__.
|
||||
|
||||
If we're lagging sufficiently, we should go back to fast syncing, but
|
||||
this is an open issue:
|
||||
https://github.com/tendermint/tendermint/issues/129
|
||||
|
|
@ -0,0 +1,75 @@
|
|||
Genesis
|
||||
=======
|
||||
|
||||
The genesis.json file in ``$TMROOT`` defines the initial TendermintCore
|
||||
state upon genesis of the blockchain (`see
|
||||
definition <https://github.com/tendermint/tendermint/blob/master/types/genesis.go>`__).
|
||||
|
||||
NOTE: This does not (yet) specify the application state (e.g. initial
|
||||
distribution of tokens). Currently we leave it up to the application to
|
||||
load the initial application genesis state. In the future, we may
|
||||
include genesis SetOption messages that get passed from TendermintCore
|
||||
to the app upon genesis.
|
||||
|
||||
Fields
|
||||
~~~~~~
|
||||
|
||||
- ``genesis_time``: Official time of blockchain start.
|
||||
- ``chain_id``: ID of the blockchain. This must be unique for every
|
||||
blockchain. If your testnet blockchains do not have unique chain IDs,
|
||||
you will have a bad time.
|
||||
- ``validators``:
|
||||
- ``pub_key``: The first element specifies the pub\_key type. 1 ==
|
||||
Ed25519. The second element are the pubkey bytes.
|
||||
- ``amount``: The validator's voting power.
|
||||
- ``name``: Name of the validator (optional).
|
||||
- ``app_hash``: The expected application hash (as returned by the
|
||||
``Commit`` ABCI message) upon genesis. If the app's hash does not
|
||||
match, a warning message is printed.
|
||||
|
||||
Sample genesis.json
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
This example is from the Basecoin mintnet example:
|
||||
|
||||
.. code:: json
|
||||
|
||||
{
|
||||
"genesis_time": "2016-02-05T06:02:31.526Z",
|
||||
"chain_id": "chain-tTH4mi",
|
||||
"validators": [
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"9BC5112CB9614D91CE423FA8744885126CD9D08D9FC9D1F42E552D662BAA411E"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach1"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"F46A5543D51F31660D9F59653B4F96061A740FF7433E0DC1ECBC30BE8494DE06"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach2"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"0E7B423C1635FD07C0FC3603B736D5D27953C1C6CA865BB9392CD79DE1A682BB"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach3"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"4F49237B9A32EB50682EDD83C48CE9CDB1D02A7CFDADCFF6EC8C1FAADB358879"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach4"
|
||||
}
|
||||
],
|
||||
"app_hash": "15005165891224E721CB664D15CB972240F5703F"
|
||||
}
|
||||
|
|
@ -1,4 +1,41 @@
|
|||
Documentation
|
||||
.. Tendermint documentation master file, created by
|
||||
sphinx-quickstart on Mon Aug 7 04:55:09 2017.
|
||||
You can adapt this file completely to your liking, but it should at least
|
||||
contain the root `toctree` directive.
|
||||
|
||||
Welcome to Tendermint's documentation!
|
||||
=====================================
|
||||
|
||||
Tendermint 101:
|
||||
|
||||
.. maxdepth set to 2 for sexiness
|
||||
.. but use 4 to upgrade documentation
|
||||
.. toctree::
|
||||
:maxdepth: 4
|
||||
|
||||
introduction.rst
|
||||
install-from-source.rst
|
||||
getting-started.rst
|
||||
deploy-testnets.rst
|
||||
using-tendermint.rst
|
||||
|
||||
Tendermint 102:
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 4
|
||||
|
||||
abci-cli.rst
|
||||
app-architecture.rst
|
||||
app-development.rst
|
||||
|
||||
Tendermint 201:
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 4
|
||||
|
||||
specification
|
||||
|
||||
Documentation (to refactor)
|
||||
-------------
|
||||
|
||||
If you're new here, start with the [Tendermint Intro](/intro).
|
||||
|
|
@ -32,3 +69,9 @@ Next Steps
|
|||
----------
|
||||
|
||||
|
||||
|
||||
|
||||
Indices and tables
|
||||
==================
|
||||
|
||||
:ref:`Keyword Index <genindex>`, :ref:`Search Page <search>`
|
||||
|
|
|
|||
|
|
@ -0,0 +1,33 @@
|
|||
Light Client Protocol
|
||||
=====================
|
||||
|
||||
Light clients are an important part of the complete blockchain system
|
||||
for most applications. Tendermint provides unique speed and security
|
||||
properties for light client applications.
|
||||
|
||||
See our developing `light-client
|
||||
repository <https://github.com/tendermint/light-client>`__.
|
||||
|
||||
Overview
|
||||
--------
|
||||
|
||||
The objective of the light client protocol is to get a
|
||||
`commit </docs/specs/validators#committing-a-block>`__ for a recent
|
||||
`block hash </docs/specs/block-structure#block-hash>`__ where the commit
|
||||
includes a majority of signatures from the last known validator set.
|
||||
From there, all the application state is verifiable with `merkle
|
||||
proofs </docs/specs/merkle-trees#iavl-tree>`__.
|
||||
|
||||
Properties
|
||||
----------
|
||||
|
||||
- You get the full collateralized security benefits of Tendermint; No
|
||||
need to wait for confirmations.
|
||||
- You get the full speed benefits of Tendermint; Transactions commit
|
||||
instantly.
|
||||
- You can get the most recent version of the application state
|
||||
non-interactively (without committing anything to the blockchain).
|
||||
For example, this means that you can get the most recent value of a
|
||||
name from the name-registry without worrying about fork censorship
|
||||
attacks, without posting a commit and waiting for confirmations. It's
|
||||
fast, secure, and free!
|
||||
|
|
@ -0,0 +1,88 @@
|
|||
Merkle
|
||||
======
|
||||
|
||||
For an overview of Merkle trees, see
|
||||
`wikipedia <https://en.wikipedia.org/wiki/Merkle_tree>`__.
|
||||
|
||||
There are two types of Merkle trees used in Tendermint.
|
||||
|
||||
- ```IAVL+ Tree`` <#iavl-tree>`__: An immutable self-balancing binary
|
||||
tree for persistent application state
|
||||
- ```Simple Tree`` <#simple-tree>`__: A simple compact binary tree for
|
||||
a static list of items
|
||||
|
||||
IAVL+ Tree
|
||||
----------
|
||||
|
||||
The purpose of this data structure is to provide persistent storage for
|
||||
key-value pairs (e.g. account state, name-registrar data, and
|
||||
per-contract data) such that a deterministic merkle root hash can be
|
||||
computed. The tree is balanced using a variant of the `AVL
|
||||
algorithm <http://en.wikipedia.org/wiki/AVL_tree>`__ so all operations
|
||||
are O(log(n)).
|
||||
|
||||
Nodes of this tree are immutable and indexed by its hash. Thus any node
|
||||
serves as an immutable snapshot which lets us stage uncommitted
|
||||
transactions from the mempool cheaply, and we can instantly roll back to
|
||||
the last committed state to process transactions of a newly committed
|
||||
block (which may not be the same set of transactions as those from the
|
||||
mempool).
|
||||
|
||||
In an AVL tree, the heights of the two child subtrees of any node differ
|
||||
by at most one. Whenever this condition is violated upon an update, the
|
||||
tree is rebalanced by creating O(log(n)) new nodes that point to
|
||||
unmodified nodes of the old tree. In the original AVL algorithm, inner
|
||||
nodes can also hold key-value pairs. The AVL+ algorithm (note the plus)
|
||||
modifies the AVL algorithm to keep all values on leaf nodes, while only
|
||||
using branch-nodes to store keys. This simplifies the algorithm while
|
||||
minimizing the size of merkle proofs
|
||||
|
||||
In Ethereum, the analog is the `Patricia
|
||||
trie <http://en.wikipedia.org/wiki/Radix_tree>`__. There are tradeoffs.
|
||||
Keys do not need to be hashed prior to insertion in IAVL+ trees, so this
|
||||
provides faster iteration in the key space which may benefit some
|
||||
applications. The logic is simpler to implement, requiring only two
|
||||
types of nodes -- inner nodes and leaf nodes. The IAVL+ tree is a binary
|
||||
tree, so merkle proofs are much shorter than the base 16 Patricia trie.
|
||||
On the other hand, while IAVL+ trees provide a deterministic merkle root
|
||||
hash, it depends on the order of updates. In practice this shouldn't be
|
||||
a problem, since you can efficiently encode the tree structure when
|
||||
serializing the tree contents.
|
||||
|
||||
Simple Tree
|
||||
-----------
|
||||
|
||||
For merkelizing smaller static lists, use the Simple Tree. The
|
||||
transactions and validation signatures of a block are hashed using this
|
||||
simple merkle tree logic.
|
||||
|
||||
If the number of items is not a power of two, the tree will not be full
|
||||
and some leaf nodes will be at different levels. Simple Tree tries to
|
||||
keep both sides of the tree the same size, but the left side may be one
|
||||
greater.
|
||||
|
||||
::
|
||||
|
||||
Simple Tree with 6 items Simple Tree with 7 items
|
||||
|
||||
* *
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
* * * *
|
||||
/ \ / \ / \ / \
|
||||
/ \ / \ / \ / \
|
||||
/ \ / \ / \ / \
|
||||
* h2 * h5 * * * h6
|
||||
/ \ / \ / \ / \ / \
|
||||
h0 h1 h3 h4 h0 h1 h2 h3 h4 h5
|
||||
|
||||
Simple Tree with Dictionaries
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The Simple Tree is used to merkelize a list of items, so to merkelize a
|
||||
(short) dictionary of key-value pairs, encode the dictionary as an
|
||||
ordered list of ``KVPair`` structs. The block hash is such a hash
|
||||
derived from all the fields of the block ``Header``. The state hash is
|
||||
similarly derived.
|
||||
|
|
@ -0,0 +1,186 @@
|
|||
RPC
|
||||
===
|
||||
|
||||
Tendermint supports the following RPC protocols:
|
||||
|
||||
- URI over HTTP
|
||||
- JSONRPC over HTTP
|
||||
- JSONRPC over websockets
|
||||
|
||||
Tendermint RPC is build using `our own RPC
|
||||
library <https://github.com/tendermint/tendermint/tree/master/rpc/lib>`__.
|
||||
Documentation and tests for that library could be found at
|
||||
``tendermint/rpc/lib`` directory.
|
||||
|
||||
Configuration
|
||||
~~~~~~~~~~~~~
|
||||
|
||||
Set the ``laddr`` config parameter under ``[rpc]`` table in the
|
||||
$TMHOME/config.toml file or the ``--rpc.laddr`` command-line flag to the
|
||||
desired protocol://host:port setting. Default: ``tcp://0.0.0.0:46657``.
|
||||
|
||||
Arguments
|
||||
~~~~~~~~~
|
||||
|
||||
Arguments which expect strings or byte arrays may be passed as quoted
|
||||
strings, like ``"abc"`` or as ``0x``-prefixed strings, like
|
||||
``0x616263``.
|
||||
|
||||
URI/HTTP
|
||||
~~~~~~~~
|
||||
|
||||
Example request:
|
||||
|
||||
.. code:: bash
|
||||
|
||||
curl -s 'http://localhost:46657/broadcast_tx_sync?tx="abc"' | jq .
|
||||
|
||||
Response:
|
||||
|
||||
.. code:: json
|
||||
|
||||
{
|
||||
"error": "",
|
||||
"result": {
|
||||
"hash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
"log": "",
|
||||
"data": "",
|
||||
"code": 0
|
||||
},
|
||||
"id": "",
|
||||
"jsonrpc": "2.0"
|
||||
}
|
||||
|
||||
The first entry in the result-array (``96``) is the method this response
|
||||
correlates with. ``96`` refers to "ResultTypeBroadcastTx", see
|
||||
`responses.go <https://github.com/tendermint/tendermint/blob/master/rpc/core/types/responses.go>`__
|
||||
for a complete overview.
|
||||
|
||||
JSONRPC/HTTP
|
||||
~~~~~~~~~~~~
|
||||
|
||||
JSONRPC requests can be POST'd to the root RPC endpoint via HTTP (e.g.
|
||||
``http://localhost:46657/``).
|
||||
|
||||
Example request:
|
||||
|
||||
.. code:: json
|
||||
|
||||
{
|
||||
"method": "broadcast_tx_sync",
|
||||
"jsonrpc": "2.0",
|
||||
"params": [ "abc" ],
|
||||
"id": "dontcare"
|
||||
}
|
||||
|
||||
JSONRPC/websockets
|
||||
~~~~~~~~~~~~~~~~~~
|
||||
|
||||
JSONRPC requests can be made via websocket. The websocket endpoint is at
|
||||
``/websocket``, e.g. ``http://localhost:46657/websocket``. Asynchronous
|
||||
RPC functions like event ``subscribe`` and ``unsubscribe`` are only
|
||||
available via websockets.
|
||||
|
||||
Endpoints
|
||||
~~~~~~~~~
|
||||
|
||||
An HTTP Get request to the root RPC endpoint (e.g.
|
||||
``http://localhost:46657``) shows a list of available endpoints.
|
||||
|
||||
::
|
||||
|
||||
Available endpoints:
|
||||
http://localhost:46657/abci_info
|
||||
http://localhost:46657/dump_consensus_state
|
||||
http://localhost:46657/genesis
|
||||
http://localhost:46657/net_info
|
||||
http://localhost:46657/num_unconfirmed_txs
|
||||
http://localhost:46657/status
|
||||
http://localhost:46657/unconfirmed_txs
|
||||
http://localhost:46657/unsafe_flush_mempool
|
||||
http://localhost:46657/unsafe_stop_cpu_profiler
|
||||
http://localhost:46657/validators
|
||||
|
||||
Endpoints that require arguments:
|
||||
http://localhost:46657/abci_query?path=_&data=_&prove=_
|
||||
http://localhost:46657/block?height=_
|
||||
http://localhost:46657/blockchain?minHeight=_&maxHeight=_
|
||||
http://localhost:46657/broadcast_tx_async?tx=_
|
||||
http://localhost:46657/broadcast_tx_commit?tx=_
|
||||
http://localhost:46657/broadcast_tx_sync?tx=_
|
||||
http://localhost:46657/commit?height=_
|
||||
http://localhost:46657/dial_seeds?seeds=_
|
||||
http://localhost:46657/subscribe?event=_
|
||||
http://localhost:46657/tx?hash=_&prove=_
|
||||
http://localhost:46657/unsafe_start_cpu_profiler?filename=_
|
||||
http://localhost:46657/unsafe_write_heap_profile?filename=_
|
||||
http://localhost:46657/unsubscribe?event=_
|
||||
|
||||
tx
|
||||
~~
|
||||
|
||||
Returns a transaction matching the given transaction hash.
|
||||
|
||||
**Parameters**
|
||||
|
||||
1. hash - the transaction hash
|
||||
2. prove - include a proof of the transaction inclusion in the block in
|
||||
the result (optional, default: false)
|
||||
|
||||
**Returns**
|
||||
|
||||
- ``proof``: the ``types.TxProof`` object
|
||||
- ``tx``: ``[]byte`` - the transaction
|
||||
- ``tx_result``: the ``abci.Result`` object
|
||||
- ``index``: ``int`` - index of the transaction
|
||||
- ``height``: ``int`` - height of the block where this transaction was
|
||||
in
|
||||
|
||||
**Example**
|
||||
|
||||
.. code:: bash
|
||||
|
||||
curl -s 'http://localhost:46657/broadcast_tx_commit?tx="abc"' | jq .
|
||||
# {
|
||||
# "error": "",
|
||||
# "result": {
|
||||
# "hash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
# "log": "",
|
||||
# "data": "",
|
||||
# "code": 0
|
||||
# },
|
||||
# "id": "",
|
||||
# "jsonrpc": "2.0"
|
||||
# }
|
||||
|
||||
curl -s 'http://localhost:46657/tx?hash=0x2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF' | jq .
|
||||
# {
|
||||
# "error": "",
|
||||
# "result": {
|
||||
# "proof": {
|
||||
# "Proof": {
|
||||
# "aunts": []
|
||||
# },
|
||||
# "Data": "YWJjZA==",
|
||||
# "RootHash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
# "Total": 1,
|
||||
# "Index": 0
|
||||
# },
|
||||
# "tx": "YWJjZA==",
|
||||
# "tx_result": {
|
||||
# "log": "",
|
||||
# "data": "",
|
||||
# "code": 0
|
||||
# },
|
||||
# "index": 0,
|
||||
# "height": 52
|
||||
# },
|
||||
# "id": "",
|
||||
# "jsonrpc": "2.0"
|
||||
# }
|
||||
|
||||
More Examples
|
||||
~~~~~~~~~~~~~
|
||||
|
||||
See the various bash tests using curl in ``test/``, and examples using
|
||||
the ``Go`` API in ``rpc/client/``.
|
||||
|
|
@ -0,0 +1,73 @@
|
|||
Secure P2P
|
||||
==========
|
||||
|
||||
The Tendermint p2p protocol uses an authenticated encryption scheme
|
||||
based on the `Station-to-Station
|
||||
Protocol <https://en.wikipedia.org/wiki/Station-to-Station_protocol>`__.
|
||||
The implementation uses
|
||||
`golang's <https://godoc.org/golang.org/x/crypto/nacl/box>`__ `nacl
|
||||
box <http://nacl.cr.yp.to/box.html>`__ for the actual authenticated
|
||||
encryption algorithm.
|
||||
|
||||
Each peer generates an ED25519 key-pair to use as a persistent
|
||||
(long-term) id.
|
||||
|
||||
When two peers establish a TCP connection, they first each generate an
|
||||
ephemeral ED25519 key-pair to use for this session, and send each other
|
||||
their respective ephemeral public keys. This happens in the clear.
|
||||
|
||||
They then each compute the shared secret. The shared secret is the
|
||||
multiplication of the peer's ephemeral private key by the other peer's
|
||||
ephemeral public key. The result is the same for both peers by the magic
|
||||
of `elliptic
|
||||
curves <https://en.wikipedia.org/wiki/Elliptic_curve_cryptography>`__.
|
||||
The shared secret is used as the symmetric key for the encryption
|
||||
algorithm.
|
||||
|
||||
The two ephemeral public keys are sorted to establish a canonical order.
|
||||
Then a 24-byte nonce is generated by concatenating the public keys and
|
||||
hashing them with Ripemd160. Note Ripemd160 produces 20byte hashes, so
|
||||
the nonce ends with four 0s.
|
||||
|
||||
The nonce is used to seed the encryption - it is critical that the same
|
||||
nonce never be used twice with the same private key. For convenience,
|
||||
the last bit of the nonce is flipped, giving us two nonces: one for
|
||||
encrypting our own messages, one for decrypting our peer's. Which ever
|
||||
peer has the higher public key uses the "bit-flipped" nonce for
|
||||
encryption.
|
||||
|
||||
Now, a challenge is generated by concatenating the ephemeral public keys
|
||||
and taking the SHA256 hash.
|
||||
|
||||
Each peer signs the challenge with their persistent private key, and
|
||||
sends the other peer an AuthSigMsg, containing their persistent public
|
||||
key and the signature. On receiving an AuthSigMsg, the peer verifies the
|
||||
signature.
|
||||
|
||||
The peers are now authenticated.
|
||||
|
||||
All future communications can now be encrypted using the shared secret
|
||||
and the generated nonces, where each nonce is incremented by one each
|
||||
time it is used. The communications maintain Perfect Forward Secrecy, as
|
||||
the persistent key pair was not used for generating secrets - only for
|
||||
authenticating.
|
||||
|
||||
Caveat
|
||||
------
|
||||
|
||||
This system is still vulnerable to a Man-In-The-Middle attack if the
|
||||
persistent public key of the remote node is not known in advance. The
|
||||
only way to mitigate this is with a public key authentication system,
|
||||
such as the Web-of-Trust or Certificate Authorities. In our case, we can
|
||||
use the blockchain itself as a certificate authority to ensure that we
|
||||
are connected to at least one validator.
|
||||
|
||||
Links
|
||||
-----
|
||||
|
||||
- `Implementation <https://github.com/tendermint/go-p2p/blob/master/secret_connection.go#L49>`__
|
||||
- `Original STS paper by Whitfield Diffie, Paul C. van Oorschot and
|
||||
Michael J.
|
||||
Wiener <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.216.6107&rep=rep1&type=pdf>`__
|
||||
- `Further work on secret
|
||||
handshakes <https://dominictarr.github.io/secret-handshake-paper/shs.pdf>`__
|
||||
|
|
@ -0,0 +1,21 @@
|
|||
#############
|
||||
Specification
|
||||
#############
|
||||
|
||||
Here you'll details of the Tendermint specification. See `the spec repo <https://github.com/tendermint/spec>`__ for upcoming material. Tendermint's types are produced by `godoc <https://godoc.org/github.com/tendermint/tendermint/types>`__
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 2
|
||||
|
||||
block-structure.rst
|
||||
byzantine-consensus-algorithm.rst
|
||||
configuration.rst
|
||||
fast-sync.rst
|
||||
genesis.rst
|
||||
light-client-protocol.rst
|
||||
merkle.rst
|
||||
rpc.rst
|
||||
secure-p2p.rst
|
||||
tendermint-types.rst
|
||||
validators.rst
|
||||
wire-protocol.rst
|
||||
|
|
@ -1,168 +0,0 @@
|
|||
# Block Structure
|
||||
|
||||
The tendermint consensus engine records all agreements by a supermajority of
|
||||
nodes into a blockchain, which is replicated among all nodes. This blockchain
|
||||
is accessible via various rpc endpoints, mainly `/block?height=` to get the full
|
||||
block, as well as `/blockchain?minHeight=_&maxHeight=_` to get a list of headers.
|
||||
But what exactly is stored in these blocks?
|
||||
|
||||
### Block
|
||||
|
||||
A [Block](https://godoc.org/github.com/tendermint/tendermint/types#Block) contains:
|
||||
|
||||
* a [Header](#header) contains merkle hashes for various chain states
|
||||
* the [Data](https://godoc.org/github.com/tendermint/tendermint/types#Data) is all transactions which are to be processed
|
||||
* the [LastCommit](#commit) > 2/3 signatures for the last block
|
||||
|
||||
The signatures returned along with block `H` are those validating block `H-1`.
|
||||
This can be a little confusing, but we must also consider that the
|
||||
`Header` also contains the `LastCommitHash`.
|
||||
It would be impossible for a Header to include the commits that sign it, as it
|
||||
would cause an infinite loop here. But when we get block `H`, we find
|
||||
`Header.LastCommitHash`, which must match the hash of `LastCommit`.
|
||||
|
||||
### Header
|
||||
|
||||
The [Header](https://godoc.org/github.com/tendermint/tendermint/types#Header) contains lots of information (follow
|
||||
link for up-to-date info). Notably, it maintains the `Height`, the `LastBlockID`
|
||||
(to make it a chain), and hashes of the data, the app state, and the validator set.
|
||||
This is important as the only item that is signed by the validators is the `Header`,
|
||||
and all other data must be validated against one of the merkle hashes in the `Header`.
|
||||
|
||||
The `DataHash` can provide a nice check on the [Data](https://godoc.org/github.com/tendermint/tendermint/types#Data)
|
||||
returned in this same block. If you are subscribed to new blocks, via tendermint RPC, in order to display or process the new transactions
|
||||
you should at least validate that the `DataHash` is valid.
|
||||
If it is important to verify autheniticity, you must wait for the `LastCommit` from the next block to make sure the block header (including `DataHash`) was properly signed.
|
||||
|
||||
The `ValidatorHash` contains a hash of the current
|
||||
[Validators](https://godoc.org/github.com/tendermint/tendermint/types#Validator). Tracking all changes in the
|
||||
validator set is complex, but a client can quickly compare this hash
|
||||
with the [hash of the currently known validators](https://godoc.org/github.com/tendermint/tendermint/types#ValidatorSet.Hash)
|
||||
to see if there have been changes.
|
||||
|
||||
The `AppHash` serves as the basis for validating any merkle proofs that come
|
||||
from the [ABCI application](https://github.com/tendermint/abci). It represents
|
||||
the state of the actual application, rather that the state of the blockchain
|
||||
itself. This means it's necessary in order to perform any business logic,
|
||||
such as verifying and account balance.
|
||||
|
||||
**Note** After the transactions are committed to a block, they still need to
|
||||
be processed in a separate step, which happens between the blocks. If you
|
||||
find a given transaction in the block at height `H`, the effects of running
|
||||
that transaction will be first visible in the `AppHash` from the block
|
||||
header at height `H+1`.
|
||||
|
||||
Like the `LastCommit` issue, this is a requirement of the
|
||||
immutability of the block chain, as the application only applies transactions
|
||||
*after* they are commited to the chain.
|
||||
|
||||
### Commit
|
||||
|
||||
The [Commit](https://godoc.org/github.com/tendermint/tendermint/types#Commit) contains a set of
|
||||
[Votes](https://godoc.org/github.com/tendermint/tendermint/types#Vote) that were made by the validator set to
|
||||
reach consensus on this block. This is the key to the security in any PoS
|
||||
system, and actually no data that cannot be traced back to a block header
|
||||
with a valid set of Votes can be trusted. Thus, getting the Commit data
|
||||
and verifying the votes is extremely important.
|
||||
|
||||
As mentioned above, in order to find the `precommit votes` for block header `H`,
|
||||
we need to query block `H+1`. Then we need to check the votes, make sure they
|
||||
really are for that block, and properly formatted. Much of this code is implemented
|
||||
in Go in the [light-client](https://github.com/tendermint/light-client) package.
|
||||
If you look at the code, you will notice that we need to provide the `chainID`
|
||||
of the blockchain in order to properly calculate the votes. This is to protect
|
||||
anyone from swapping votes between chains to fake (or frame) a validator.
|
||||
Also note that this `chainID` is in the `genesis.json` from _Tendermint_,
|
||||
not the `genesis.json` from the basecoin app ([that is a different chainID...](https://github.com/tendermint/basecoin/issues/32)).
|
||||
|
||||
Once we have those votes,
|
||||
and we calculated the proper [sign bytes](https://godoc.org/github.com/tendermint/tendermint/types#Vote.WriteSignBytes)
|
||||
using the chainID and a [nice helper function](https://godoc.org/github.com/tendermint/tendermint/types#SignBytes),
|
||||
we can verify them. The light client is responsible for maintaining a set of
|
||||
validators that we trust. Each vote only stores the validators `Address`, as well
|
||||
as the `Signature`. Assuming we have a local copy of the trusted validator set,
|
||||
we can look up the `Public Key` of the validator given its `Address`, then
|
||||
verify that the `Signature` matches the `SignBytes` and `Public Key`.
|
||||
Then we sum up the total voting power of all validators, whose votes fulfilled
|
||||
all these stringent requirements. If the total number of voting power for a single block is greater
|
||||
than 2/3 of all voting power, then we can finally trust the
|
||||
block header, the AppHash, and the proof we got from the ABCI application.
|
||||
|
||||
#### Vote Sign Bytes
|
||||
The `sign-bytes` of a vote is produced by taking a [`stable-json`](https://github.com/substack/json-stable-stringify)-like deterministic JSON [`wire`](/docs/specs/wire-protocol) encoding of the vote (excluding the `Signature` field), and wrapping it with `{"chain_id":"my_chain","vote":...}`.
|
||||
|
||||
For example, a precommit vote might have the following `sign-bytes`:
|
||||
|
||||
```json
|
||||
{"chain_id":"my_chain","vote":{"block_hash":"611801F57B4CE378DF1A3FFF1216656E89209A99","block_parts_header":{"hash":"B46697379DBE0774CC2C3B656083F07CA7E0F9CE","total":123},"height":1234,"round":1,"type":2}}
|
||||
```
|
||||
|
||||
### Block Hash
|
||||
|
||||
The [block hash](https://godoc.org/github.com/tendermint/tendermint/types#Block.Hash) is the [Simple Tree hash](Merkle-Trees#simple-tree-with-dictionaries) of the fields of the block `Header` encoded as a list of `KVPair`s.
|
||||
|
||||
### Transaction
|
||||
|
||||
A transaction is any sequence of bytes. It is up to your [ABCI](https://github.com/tendermint/abci) application to accept or reject transactions.
|
||||
|
||||
### BlockID
|
||||
|
||||
Many of these data structures refer to the [BlockID](https://godoc.org/github.com/tendermint/tendermint/types#BlockID),
|
||||
which is the `BlockHash` (hash of the block header, also referred to by the next block)
|
||||
along with the `PartSetHeader`. The `PartSetHeader` is explained below and is used internally
|
||||
to orchestrate the p2p propogation. For clients, it is basically opaque bytes,
|
||||
but they must match for all votes.
|
||||
|
||||
### PartSetHeader
|
||||
|
||||
The [PartSetHeader](https://godoc.org/github.com/tendermint/tendermint/types#PartSetHeader) contains the total number of pieces in a [PartSet](https://godoc.org/github.com/tendermint/tendermint/types#PartSet), and the Merkle root hash of those pieces.
|
||||
|
||||
### PartSet
|
||||
|
||||
PartSet is used to split a byteslice of data into parts (pieces) for transmission.
|
||||
By splitting data into smaller parts and computing a Merkle root hash on the list,
|
||||
you can verify that a part is legitimately part of the complete data, and the
|
||||
part can be forwarded to other peers before all the parts are known. In short,
|
||||
it's a fast way to securely propagate a large chunk of data (like a block) over a gossip network.
|
||||
|
||||
PartSet was inspired by the LibSwift project.
|
||||
|
||||
Usage:
|
||||
|
||||
```go
|
||||
data := RandBytes(2 << 20) // Something large
|
||||
|
||||
partSet := NewPartSetFromData(data)
|
||||
partSet.Total() // Total number of 4KB parts
|
||||
partSet.Count() // Equal to the Total, since we already have all the parts
|
||||
partSet.Hash() // The Merkle root hash
|
||||
partSet.BitArray() // A BitArray of partSet.Total() 1's
|
||||
|
||||
header := partSet.Header() // Send this to the peer
|
||||
header.Total // Total number of parts
|
||||
header.Hash // The merkle root hash
|
||||
|
||||
// Now we'll reconstruct the data from the parts
|
||||
partSet2 := NewPartSetFromHeader(header)
|
||||
partSet2.Total() // Same total as partSet.Total()
|
||||
partSet2.Count() // Zero, since this PartSet doesn't have any parts yet.
|
||||
partSet2.Hash() // Same hash as in partSet.Hash()
|
||||
partSet2.BitArray() // A BitArray of partSet.Total() 0's
|
||||
|
||||
// In a gossip network the parts would arrive in arbitrary order, perhaps
|
||||
// in response to explicit requests for parts, or optimistically in response
|
||||
// to the receiving peer's partSet.BitArray().
|
||||
for !partSet2.IsComplete() {
|
||||
part := receivePartFromGossipNetwork()
|
||||
added, err := partSet2.AddPart(part)
|
||||
if err != nil {
|
||||
// A wrong part,
|
||||
// the merkle trail does not hash to partSet2.Hash()
|
||||
} else if !added {
|
||||
// A duplicate part already received
|
||||
}
|
||||
}
|
||||
|
||||
data2, _ := ioutil.ReadAll(partSet2.GetReader())
|
||||
bytes.Equal(data, data2) // true
|
||||
```
|
||||
|
|
@ -1,191 +0,0 @@
|
|||
# Byzantine Consensus Algorithm
|
||||
|
||||
_The draft 0.6 whitepaper is outdated. The new algorithm is detailed below. See [revisions](#revisions)_
|
||||
|
||||
## Terms
|
||||
- The network is composed of optionally connected _nodes_. Nodes directly connected to a particular node are called _peers_.
|
||||
- The consensus process in deciding the next block (at some _height_ `H`) is composed of one or many _rounds_.
|
||||
- `NewHeight`, `Propose`, `Prevote`, `Precommit`, and `Commit` represent state machine states of a round. (aka `RoundStep` or just "step").
|
||||
- A node is said to be _at_ a given height, round, and step, or at `(H,R,S)`, or at `(H,R)` in short to omit the step.
|
||||
- To _prevote_ or _precommit_ something means to broadcast a [prevote vote](https://godoc.org/github.com/tendermint/tendermint/types#Vote) or [first precommit vote](https://godoc.org/github.com/tendermint/tendermint/types#FirstPrecommit) for something.
|
||||
- A vote _at_ `(H,R)` is a vote signed with the bytes for `H` and `R` included in its [`sign-bytes`](/docs/specs/block-structure#vote-sign-bytes).
|
||||
- _+2/3_ is short for "more than 2/3"
|
||||
- _1/3+_ is short for "1/3 or more"
|
||||
- A set of +2/3 of prevotes for a particular block or `<nil>` at `(H,R)` is called a _proof-of-lock-change_ or _PoLC_ for short.
|
||||
|
||||
## State Machine Overview
|
||||
|
||||
At each height of the blockchain a round-based protocol is run to determine
|
||||
the next block. Each round is composed of three _steps_ (`Propose`, `Prevote`, and
|
||||
`Precommit`), along with two special steps `Commit` and `NewHeight`.
|
||||
|
||||
In the optimal scenario, the order of steps is:
|
||||
|
||||
```
|
||||
NewHeight -> (Propose -> Prevote -> Precommit)+ -> Commit -> NewHeight ->...
|
||||
```
|
||||
|
||||
The sequence `(Propose -> Prevote -> Precommit)` is called a _round_. There may be more than one round required to commit a block at a given height. Examples for why more rounds may be required include:
|
||||
|
||||
- The designated proposer was not online.
|
||||
- The block proposed by the designated proposer was not valid.
|
||||
- The block proposed by the designated proposer did not propagate in time.
|
||||
- The block proposed was valid, but +2/3 of prevotes for the proposed block were not received in time for enough validator nodes by the time they reached the `Precommit` step. Even though +2/3 of prevotes are necessary to progress to the next step, at least one validator may have voted `<nil>` or maliciously voted for something else.
|
||||
- The block proposed was valid, and +2/3 of prevotes were received for enough nodes, but +2/3 of precommits for the proposed block were not received for enough validator nodes.
|
||||
|
||||
Some of these problems are resolved by moving onto the next round & proposer. Others are resolved by increasing certain round timeout parameters over each successive round.
|
||||
|
||||
## State Machine Diagram
|
||||
|
||||
```
|
||||
+-------------------------------------+
|
||||
v |(Wait til `CommmitTime+timeoutCommit`)
|
||||
+-----------+ +-----+-----+
|
||||
+----------> | Propose +--------------+ | NewHeight |
|
||||
| +-----------+ | +-----------+
|
||||
| | ^
|
||||
|(Else, after timeoutPrecommit) v |
|
||||
+-----+-----+ +-----------+ |
|
||||
| Precommit | <------------------------+ Prevote | |
|
||||
+-----+-----+ +-----------+ |
|
||||
|(When +2/3 Precommits for block found) |
|
||||
v |
|
||||
+--------------------------------------------------------------------+
|
||||
| Commit |
|
||||
| |
|
||||
| * Set CommitTime = now; |
|
||||
| * Wait for block, then stage/save/commit block; |
|
||||
+--------------------------------------------------------------------+
|
||||
```
|
||||
|
||||
## Background Gossip
|
||||
|
||||
A node may not have a corresponding validator private key, but it nevertheless plays an active role in the consensus process by relaying relevant meta-data, proposals, blocks, and votes to its peers. A node that has the private keys of an active validator and is engaged in signing votes is called a _validator-node_. All nodes (not just validator-nodes) have an associated state (the current height, round, and step) and work to make progress.
|
||||
|
||||
Between two nodes there exists a `Connection`, and multiplexed on top of this connection are fairly throttled `Channel`s of information. An epidemic gossip protocol is implemented among some of these channels to bring peers up to speed on the most recent state of consensus. For example,
|
||||
|
||||
- Nodes gossip `PartSet` parts of the current round's proposer's proposed block. A LibSwift inspired algorithm is used to quickly broadcast blocks across the gossip network.
|
||||
- Nodes gossip prevote/precommit votes. A node NODE_A that is ahead of NODE_B can send NODE_B prevotes or precommits for NODE_B's current (or future) round to enable it to progress forward.
|
||||
- Nodes gossip prevotes for the proposed PoLC (proof-of-lock-change) round if one is proposed.
|
||||
- Nodes gossip to nodes lagging in blockchain height with block [commits](https://godoc.org/github.com/tendermint/tendermint/types#Commit) for older blocks.
|
||||
- Nodes opportunistically gossip `HasVote` messages to hint peers what votes it already has.
|
||||
- Nodes broadcast their current state to all neighboring peers. (but is not gossiped further)
|
||||
|
||||
There's more, but let's not get ahead of ourselves here.
|
||||
|
||||
## Proposals
|
||||
|
||||
A proposal is signed and published by the designated proposer at each round. The proposer is chosen by a deterministic and non-choking round robin selection algorithm that selects proposers in proportion to their voting power. (see [implementation](https://github.com/tendermint/tendermint/blob/develop/types/validator_set.go))
|
||||
|
||||
A proposal at `(H,R)` is composed of a block and an optional latest `PoLC-Round < R` which is included iff the proposer knows of one. This hints the network to allow nodes to unlock (when safe) to ensure the liveness property.
|
||||
|
||||
## State Machine Spec
|
||||
|
||||
### Propose Step (height:H,round:R)
|
||||
Upon entering `Propose`:
|
||||
- The designated proposer proposes a block at `(H,R)`.
|
||||
|
||||
The `Propose` step ends:
|
||||
- After `timeoutProposeR` after entering `Propose`. --> goto `Prevote(H,R)`
|
||||
- After receiving proposal block and all prevotes at `PoLC-Round`. --> goto `Prevote(H,R)`
|
||||
- After [common exit conditions](#common-exit-conditions)
|
||||
|
||||
### Prevote Step (height:H,round:R)
|
||||
Upon entering `Prevote`, each validator broadcasts its prevote vote.
|
||||
|
||||
- First, if the validator is locked on a block since `LastLockRound` but now has a PoLC for something else at round `PoLC-Round` where `LastLockRound < PoLC-Round < R`, then it unlocks.
|
||||
- If the validator is still locked on a block, it prevotes that.
|
||||
- Else, if the proposed block from `Propose(H,R)` is good, it prevotes that.
|
||||
- Else, if the proposal is invalid or wasn't received on time, it prevotes `<nil>`.
|
||||
|
||||
The `Prevote` step ends:
|
||||
- After +2/3 prevotes for a particular block or `<nil>`. --> goto `Precommit(H,R)`
|
||||
- After `timeoutPrevote` after receiving any +2/3 prevotes. --> goto `Precommit(H,R)`
|
||||
- After [common exit conditions](#common-exit-conditions)
|
||||
|
||||
### Precommit Step (height:H,round:R)
|
||||
Upon entering `Precommit`, each validator broadcasts its precommit vote.
|
||||
- If the validator has a PoLC at `(H,R)` for a particular block `B`, it (re)locks (or changes lock to) and precommits `B` and sets `LastLockRound = R`.
|
||||
- Else, if the validator has a PoLC at `(H,R)` for `<nil>`, it unlocks and precommits `<nil>`.
|
||||
- Else, it keeps the lock unchanged and precommits `<nil>`.
|
||||
|
||||
A precommit for `<nil>` means "I didn’t see a PoLC for this round, but I did get +2/3 prevotes and waited a bit".
|
||||
|
||||
The Precommit step ends:
|
||||
- After +2/3 precommits for `<nil>`. --> goto `Propose(H,R+1)`
|
||||
- After `timeoutPrecommit` after receiving any +2/3 precommits. --> goto `Propose(H,R+1)`
|
||||
- After [common exit conditions](#common-exit-conditions)
|
||||
|
||||
#### common exit conditions
|
||||
- After +2/3 precommits for a particular block. --> goto `Commit(H)`
|
||||
- After any +2/3 prevotes received at `(H,R+x)`. --> goto `Prevote(H,R+x)`
|
||||
- After any +2/3 precommits received at `(H,R+x)`. --> goto `Precommit(H,R+x)`
|
||||
|
||||
### Commit Step (height:H)
|
||||
- Set `CommitTime = now()`
|
||||
- Wait until block is received. --> goto `NewHeight(H+1)`
|
||||
|
||||
### NewHeight Step (height:H)
|
||||
- Move `Precommits` to `LastCommit` and increment height.
|
||||
- Set `StartTime = CommitTime+timeoutCommit`
|
||||
- Wait until `StartTime` to receive straggler commits. --> goto `Propose(H,0)`
|
||||
|
||||
## Proofs
|
||||
|
||||
### Proof of Safety
|
||||
Assume that at most -1/3 of the voting power of validators is byzantine. If a validator commits block `B` at round `R`, it's because it saw +2/3 of precommits at round `R`. This implies that 1/3+ of honest nodes are still locked at round `R' > R`. These locked validators will remain locked until they see a PoLC at `R' > R`, but this won't happen because 1/3+ are locked and honest, so at most -2/3 are available to vote for anything other than `B`.
|
||||
|
||||
### Proof of Liveness
|
||||
If 1/3+ honest validators are locked on two different blocks from different rounds, a proposers' `PoLC-Round` will eventually cause nodes locked from the earlier round to unlock. Eventually, the designated proposer will be one that is aware of a PoLC at the later round. Also, `timeoutProposalR` increments with round `R`, while the size of a proposal are capped, so eventually the network is able to "fully gossip" the whole proposal (e.g. the block & PoLC).
|
||||
|
||||
### Proof of Fork Accountability
|
||||
Define the JSet (justification-vote-set) at height `H` of a validator `V1` to be all the votes signed by the validator at `H` along with justification PoLC prevotes for each lock change. For example, if `V1` signed the following precommits: `Precommit(B1 @ round 0)`, `Precommit(<nil> @ round 1)`, `Precommit(B2 @ round 4)` (note that no precommits were signed for rounds 2 and 3, and that's ok), `Precommit(B1 @ round 0)` must be justified by a PoLC at round 0, and `Precommit(B2 @ round 4)` must be justified by a PoLC at round 4; but the precommit for `<nil>` at round 1 is not a lock-change by definition so the JSet for `V1` need not include any prevotes at round 1, 2, or 3 (unless `V1` happened to have prevoted for those rounds).
|
||||
|
||||
Further, define the JSet at height `H` of a set of validators `VSet` to be the union of the JSets for each validator in `VSet`. For a given commit by honest validators at round `R` for block `B` we can construct a JSet to justify the commit for `B` at `R`.
|
||||
We say that a JSet _justifies_ a commit at `(H,R)` if all the committers (validators in the commit-set) are each justified in the JSet with no duplicitous vote signatures (by the committers).
|
||||
|
||||
- **Lemma**: When a fork is detected by the existence of two conflicting [commits](/docs/specs/validators#commiting-a-block), the union of the JSets for both commits (if they can be compiled) must include double-signing by at least 1/3+ of the validator set. **Proof**: The commit cannot be at the same round, because that would immediately imply double-signing by 1/3+. Take the union of the JSets of both commits. If there is no double-signing by at least 1/3+ of the validator set in the union, then no honest validator could have precommitted any different block after the first commit. Yet, +2/3 did. Reductio ad absurdum.
|
||||
|
||||
As a corollary, when there is a fork, an external process can determine the blame by requiring each validator to justify all of its round votes. Either we will find 1/3+ who cannot justify at least one of their votes, and/or, we will find 1/3+ who had double-signed.
|
||||
|
||||
### Alternative algorithm
|
||||
|
||||
Alternatively, we can take the JSet of a commit to be the "full commit". That is, if light clients and validators do not consider a block to be committed unless the JSet of the commit is also known, then we get the desirable property that if there ever is a fork (e.g. there are two conflicting "full commits"), then 1/3+ of the validators are immediately punishable for double-signing.
|
||||
|
||||
There are many ways to ensure that the gossip network efficiently share the JSet of a commit. One solution is to add a new message type that tells peers that this node has (or does not have) a +2/3 majority for B (or <nil>) at (H,R), and a bitarray of which votes contributed towards that majority. Peers can react by responding with appropriate votes.
|
||||
|
||||
We will implement such an algorithm for the next iteration of the Tendermint consensus protocol.
|
||||
|
||||
Other potential improvements include adding more data in votes such as the last known PoLC round that caused a lock change, and the last voted round/step (or, we may require that validators not skip any votes). This may make JSet verification/gossip logic easier to implement.
|
||||
|
||||
### Censorship Attacks
|
||||
|
||||
Due to the definition of a block [commit](/docs/specs/validators#commiting-a-block), any 1/3+ coalition of validators can halt the blockchain by not broadcasting their votes. Such a coalition can also censor particular transactions by rejecting blocks that include these transactions, though this would result in a significant proportion of block proposals to be rejected, which would slow down the rate of block commits of the blockchain, reducing its utility and value. The malicious coalition might also broadcast votes in a trickle so as to grind blockchain block commits to a near halt, or engage in any combination of these attacks.
|
||||
|
||||
If a global active adversary were also involved, it can partition the network in such a way that it may appear that the wrong subset of validators were responsible for the slowdown. This is not just a limitation of Tendermint, but rather a limitation of all consensus protocols whose network is potentially controlled by an active adversary.
|
||||
|
||||
### Overcoming Forks and Censorship Attacks
|
||||
|
||||
For these types of attacks, a subset of the validators through external means
|
||||
should coordinate to sign a reorg-proposal that chooses a fork (and any evidence
|
||||
thereof) and the initial subset of validators with their signatures. Validators
|
||||
who sign such a reorg-proposal forego its collateral on all other forks.
|
||||
Clients should verify the signatures on the reorg-proposal, verify any evidence,
|
||||
and make a judgement or prompt the end-user for a decision. For example, a
|
||||
phone wallet app may prompt the user with a security warning, while a
|
||||
refrigerator may accept any reorg-proposal signed by +½ of the original
|
||||
validators.
|
||||
|
||||
No non-synchronous Byzantine fault-tolerant algorithm can come to consensus when
|
||||
⅓+ of validators are dishonest, yet a fork assumes that ⅓+ of validators have
|
||||
already been dishonest by double-signing or lock-changing without justification.
|
||||
So, signing the reorg-proposal is a coordination problem that cannot be solved
|
||||
by any non-synchronous protocol (i.e. automatically, and without making
|
||||
assumptions about the reliability of the underlying network). It must be
|
||||
provided by means external to the weakly-synchronous Tendermint consensus
|
||||
algorithm. For now, we leave the problem of reorg-proposal coordination to
|
||||
human coordination via internet media. Validators must take care to ensure that
|
||||
there are no significant network partitions, to avoid situations where two
|
||||
conflicting reorg-proposals are signed.
|
||||
|
||||
Assuming that the external coordination medium and protocol is robust, it follows that forks are less of a concern than [censorship attacks](#censorship-attacks).
|
||||
|
|
@ -1,36 +0,0 @@
|
|||
# Configuration
|
||||
|
||||
TendermintCore can be configured via a TOML file in `$TMHOME/config.toml`.
|
||||
Some of these parameters can be overridden by command-line flags.
|
||||
|
||||
### Config parameters
|
||||
|
||||
The main config parameters are defined [here](https://github.com/tendermint/tendermint/blob/master/config/config.go).
|
||||
|
||||
* `abci`: ABCI transport (socket | grpc). _Default_: `socket`
|
||||
* `db_backend`: Database backend for the blockchain and TendermintCore state. `leveldb` or `memdb`. _Default_: `"leveldb"`
|
||||
* `db_dir`: Database dir. _Default_: `"$TMHOME/data"`
|
||||
* `fast_sync`: Whether to sync faster from the block pool. _Default_: `true`
|
||||
* `genesis_file`: The location of the genesis file. _Default_: `"$TMHOME/genesis.json"`
|
||||
* `log_level`: _Default_: `"state:info,*:error"`
|
||||
* `moniker`: Name of this node. _Default_: `"anonymous"`
|
||||
* `priv_validator_file`: Validator private key file. _Default_: `"$TMHOME/priv_validator.json"`
|
||||
* `prof_laddr`: Profile listen address. _Default_: `""`
|
||||
* `proxy_app`: The ABCI app endpoint. _Default_: `"tcp://127.0.0.1:46658"`
|
||||
|
||||
* `consensus.max_block_size_txs`: Maximum number of block txs. _Default_: `10000`
|
||||
* `consensus.timeout_*`: Various consensus timeout parameters **TODO**
|
||||
* `consensus.wal_file`: Consensus state WAL. _Default_: `"$TMHOME/data/cswal"`
|
||||
* `consensus.wal_light`: Whether to use light-mode for Consensus state WAL. _Default_: `false`
|
||||
|
||||
* `mempool.*`: Various mempool parameters **TODO**
|
||||
|
||||
* `p2p.addr_book_file`: Peer address book. _Default_: `"$TMHOME/addrbook.json"`. **NOT USED**
|
||||
* `p2p.laddr`: Node listen address. (0.0.0.0:0 means any interface, any port). _Default_: `"0.0.0.0:46656"`
|
||||
* `p2p.pex`: Enable Peer-Exchange (dev feature). _Default_: `false`
|
||||
* `p2p.seeds`: Comma delimited host:port seed nodes. _Default_: `""`
|
||||
* `p2p.skip_upnp`: Skip UPNP detection. _Default_: `false`
|
||||
|
||||
* `rpc.grpc_laddr`: GRPC listen address (BroadcastTx only). Port required. _Default_: `""`
|
||||
* `rpc.laddr`: RPC listen address. Port required. _Default_: `"0.0.0.0:46657"`
|
||||
* `rpc.unsafe`: Enabled unsafe rpc methods. _Default_: `true`
|
||||
|
|
@ -1,13 +0,0 @@
|
|||
# Fast Sync
|
||||
|
||||
## Background
|
||||
|
||||
In a proof of work blockchain, syncing with the chain is the same process as staying up-to-date with the consensus: download blocks, and look for the one with the most total work. In proof-of-stake, the consensus process is more complex, as it involves rounds of communication between the nodes to determine what block should be committed next. Using this process to sync up with the blockchain from scratch can take a very long time. It's much faster to just download blocks and check the merkle tree of validators than to run the real-time consensus gossip protocol.
|
||||
|
||||
## Fast Sync
|
||||
|
||||
To support faster syncing, tendermint offers a `fast-sync` mode, which is enabled by default, and can be toggled in the `config.toml` or via `--fast_sync=false`.
|
||||
|
||||
In this mode, the tendermint daemon will sync hundreds of times faster than if it used the real-time consensus process. Once caught up, the daemon will switch out of fast sync and into the normal consensus mode. After running for some time, the node is considered `caught up` if it has at least one peer and it's height is at least as high as the max reported peer height. See [the IsCaughtUp method](https://github.com/tendermint/tendermint/blob/b467515719e686e4678e6da4e102f32a491b85a0/blockchain/pool.go#L128).
|
||||
|
||||
If we're lagging sufficiently, we should go back to fast syncing, but this is an open issue: https://github.com/tendermint/tendermint/issues/129
|
||||
|
|
@ -1,61 +0,0 @@
|
|||
# Genesis
|
||||
|
||||
The genesis.json file in `$TMROOT` defines the initial TendermintCore state upon genesis of the blockchain ([see definition](https://github.com/tendermint/tendermint/blob/master/types/genesis.go)).
|
||||
|
||||
NOTE: This does not (yet) specify the application state (e.g. initial distribution of tokens). Currently we leave it up to the application to load the initial application genesis state. In the future, we may include genesis SetOption messages that get passed from TendermintCore to the app upon genesis.
|
||||
|
||||
### Fields
|
||||
|
||||
* `genesis_time`: Official time of blockchain start.
|
||||
* `chain_id`: ID of the blockchain. This must be unique for every blockchain. If your testnet blockchains do not have unique chain IDs, you will have a bad time.
|
||||
* `validators`:
|
||||
* `pub_key`: The first element specifies the pub_key type. 1 == Ed25519. The second element are the pubkey bytes.
|
||||
* `amount`: The validator's voting power.
|
||||
* `name`: Name of the validator (optional).
|
||||
* `app_hash`: The expected application hash (as returned by the `Commit` ABCI message) upon genesis. If the app's hash does not match, a warning message is printed.
|
||||
|
||||
### Sample genesis.json
|
||||
|
||||
This example is from the Basecoin mintnet example:
|
||||
|
||||
```json
|
||||
{
|
||||
"genesis_time": "2016-02-05T06:02:31.526Z",
|
||||
"chain_id": "chain-tTH4mi",
|
||||
"validators": [
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"9BC5112CB9614D91CE423FA8744885126CD9D08D9FC9D1F42E552D662BAA411E"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach1"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"F46A5543D51F31660D9F59653B4F96061A740FF7433E0DC1ECBC30BE8494DE06"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach2"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"0E7B423C1635FD07C0FC3603B736D5D27953C1C6CA865BB9392CD79DE1A682BB"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach3"
|
||||
},
|
||||
{
|
||||
"pub_key": [
|
||||
1,
|
||||
"4F49237B9A32EB50682EDD83C48CE9CDB1D02A7CFDADCFF6EC8C1FAADB358879"
|
||||
],
|
||||
"amount": 1,
|
||||
"name": "mach4"
|
||||
}
|
||||
],
|
||||
"app_hash": "15005165891224E721CB664D15CB972240F5703F"
|
||||
}
|
||||
```
|
||||
|
|
@ -1,15 +0,0 @@
|
|||
# Light Client Protocol
|
||||
|
||||
Light clients are an important part of the complete blockchain system for most applications. Tendermint provides unique speed and security properties for light client applications.
|
||||
|
||||
See our developing [light-client repository](https://github.com/tendermint/light-client).
|
||||
|
||||
## Overview
|
||||
|
||||
The objective of the light client protocol is to get a [commit](/docs/specs/validators#committing-a-block) for a recent [block hash](/docs/specs/block-structure#block-hash) where the commit includes a majority of signatures from the last known validator set. From there, all the application state is verifiable with [merkle proofs](/docs/specs/merkle-trees#iavl-tree).
|
||||
|
||||
## Properties
|
||||
|
||||
- You get the full collateralized security benefits of Tendermint; No need to wait for confirmations.
|
||||
- You get the full speed benefits of Tendermint; Transactions commit instantly.
|
||||
- You can get the most recent version of the application state non-interactively (without committing anything to the blockchain). For example, this means that you can get the most recent value of a name from the name-registry without worrying about fork censorship attacks, without posting a commit and waiting for confirmations. It's fast, secure, and free!
|
||||
|
|
@ -1,45 +0,0 @@
|
|||
# Merkle
|
||||
|
||||
For an overview of Merkle trees, see [wikipedia](https://en.wikipedia.org/wiki/Merkle_tree).
|
||||
|
||||
There are two types of Merkle trees used in Tendermint.
|
||||
|
||||
- [`IAVL+ Tree`](#iavl-tree): An immutable self-balancing binary tree for persistent application state
|
||||
- [`Simple Tree`](#simple-tree): A simple compact binary tree for a static list of items
|
||||
|
||||
## IAVL+ Tree
|
||||
|
||||
The purpose of this data structure is to provide persistent storage for key-value pairs (e.g. account state, name-registrar data, and per-contract data) such that a deterministic merkle root hash can be computed. The tree is balanced using a variant of the [AVL algorithm](http://en.wikipedia.org/wiki/AVL_tree) so all operations are O(log(n)).
|
||||
|
||||
Nodes of this tree are immutable and indexed by its hash. Thus any node serves as an immutable snapshot which lets us stage uncommitted transactions from the mempool cheaply, and we can instantly roll back to the last committed state to process transactions of a newly committed block (which may not be the same set of transactions as those from the mempool).
|
||||
|
||||
In an AVL tree, the heights of the two child subtrees of any node differ by at most one. Whenever this condition is violated upon an update, the tree is rebalanced by creating O(log(n)) new nodes that point to unmodified nodes of the old tree. In the original AVL algorithm, inner nodes can also hold key-value pairs. The AVL+ algorithm (note the plus) modifies the AVL algorithm to keep all values on leaf nodes, while only using branch-nodes to store keys. This simplifies the algorithm while minimizing the size of merkle proofs
|
||||
|
||||
In Ethereum, the analog is the [Patricia trie](http://en.wikipedia.org/wiki/Radix_tree). There are tradeoffs. Keys do not need to be hashed prior to insertion in IAVL+ trees, so this provides faster iteration in the key space which may benefit some applications. The logic is simpler to implement, requiring only two types of nodes -- inner nodes and leaf nodes. The IAVL+ tree is a binary tree, so merkle proofs are much shorter than the base 16 Patricia trie. On the other hand, while IAVL+ trees provide a deterministic merkle root hash, it depends on the order of updates. In practice this shouldn't be a problem, since you can efficiently encode the tree structure when serializing the tree contents.
|
||||
|
||||
## Simple Tree
|
||||
|
||||
For merkelizing smaller static lists, use the Simple Tree. The transactions and validation signatures of a block are hashed using this simple merkle tree logic.
|
||||
|
||||
If the number of items is not a power of two, the tree will not be full and some leaf nodes will be at different levels. Simple Tree tries to keep both sides of the tree the same size, but the left side may be one greater.
|
||||
|
||||
```
|
||||
Simple Tree with 6 items Simple Tree with 7 items
|
||||
|
||||
* *
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
/ \ / \
|
||||
* * * *
|
||||
/ \ / \ / \ / \
|
||||
/ \ / \ / \ / \
|
||||
/ \ / \ / \ / \
|
||||
* h2 * h5 * * * h6
|
||||
/ \ / \ / \ / \ / \
|
||||
h0 h1 h3 h4 h0 h1 h2 h3 h4 h5
|
||||
```
|
||||
|
||||
### Simple Tree with Dictionaries
|
||||
|
||||
The Simple Tree is used to merkelize a list of items, so to merkelize a (short) dictionary of key-value pairs, encode the dictionary as an ordered list of `KVPair` structs. The block hash is such a hash derived from all the fields of the block `Header`. The state hash is similarly derived.
|
||||
|
|
@ -1,156 +0,0 @@
|
|||
# RPC
|
||||
|
||||
Tendermint supports the following RPC protocols:
|
||||
|
||||
* URI over HTTP
|
||||
* JSONRPC over HTTP
|
||||
* JSONRPC over websockets
|
||||
|
||||
Tendermint RPC is build using [our own RPC library](https://github.com/tendermint/tendermint/tree/master/rpc/lib). Documentation and tests for that library could be found at `tendermint/rpc/lib` directory.
|
||||
|
||||
### Configuration
|
||||
|
||||
Set the `laddr` config parameter under `[rpc]` table in the $TMHOME/config.toml file or the `--rpc.laddr` command-line flag to the desired protocol://host:port setting. Default: `tcp://0.0.0.0:46657`.
|
||||
|
||||
### Arguments
|
||||
|
||||
Arguments which expect strings or byte arrays may be passed as quoted strings, like `"abc"` or as `0x`-prefixed strings, like `0x616263`.
|
||||
|
||||
### URI/HTTP
|
||||
|
||||
Example request:
|
||||
```bash
|
||||
curl -s 'http://localhost:46657/broadcast_tx_sync?tx="abc"' | jq .
|
||||
```
|
||||
|
||||
Response:
|
||||
```json
|
||||
{
|
||||
"error": "",
|
||||
"result": {
|
||||
"hash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
"log": "",
|
||||
"data": "",
|
||||
"code": 0
|
||||
},
|
||||
"id": "",
|
||||
"jsonrpc": "2.0"
|
||||
}
|
||||
```
|
||||
|
||||
The first entry in the result-array (`96`) is the method this response correlates with. `96` refers to "ResultTypeBroadcastTx", see [responses.go](https://github.com/tendermint/tendermint/blob/master/rpc/core/types/responses.go) for a complete overview.
|
||||
|
||||
### JSONRPC/HTTP
|
||||
|
||||
JSONRPC requests can be POST'd to the root RPC endpoint via HTTP (e.g. `http://localhost:46657/`).
|
||||
|
||||
Example request:
|
||||
```json
|
||||
{
|
||||
"method": "broadcast_tx_sync",
|
||||
"jsonrpc": "2.0",
|
||||
"params": [ "abc" ],
|
||||
"id": "dontcare"
|
||||
}
|
||||
```
|
||||
|
||||
### JSONRPC/websockets
|
||||
|
||||
JSONRPC requests can be made via websocket. The websocket endpoint is at `/websocket`, e.g. `http://localhost:46657/websocket`. Asynchronous RPC functions like event `subscribe` and `unsubscribe` are only available via websockets.
|
||||
|
||||
### Endpoints
|
||||
|
||||
An HTTP Get request to the root RPC endpoint (e.g. `http://localhost:46657`) shows a list of available endpoints.
|
||||
|
||||
```
|
||||
Available endpoints:
|
||||
http://localhost:46657/abci_info
|
||||
http://localhost:46657/dump_consensus_state
|
||||
http://localhost:46657/genesis
|
||||
http://localhost:46657/net_info
|
||||
http://localhost:46657/num_unconfirmed_txs
|
||||
http://localhost:46657/status
|
||||
http://localhost:46657/unconfirmed_txs
|
||||
http://localhost:46657/unsafe_flush_mempool
|
||||
http://localhost:46657/unsafe_stop_cpu_profiler
|
||||
http://localhost:46657/validators
|
||||
|
||||
Endpoints that require arguments:
|
||||
http://localhost:46657/abci_query?path=_&data=_&prove=_
|
||||
http://localhost:46657/block?height=_
|
||||
http://localhost:46657/blockchain?minHeight=_&maxHeight=_
|
||||
http://localhost:46657/broadcast_tx_async?tx=_
|
||||
http://localhost:46657/broadcast_tx_commit?tx=_
|
||||
http://localhost:46657/broadcast_tx_sync?tx=_
|
||||
http://localhost:46657/commit?height=_
|
||||
http://localhost:46657/dial_seeds?seeds=_
|
||||
http://localhost:46657/subscribe?event=_
|
||||
http://localhost:46657/tx?hash=_&prove=_
|
||||
http://localhost:46657/unsafe_start_cpu_profiler?filename=_
|
||||
http://localhost:46657/unsafe_write_heap_profile?filename=_
|
||||
http://localhost:46657/unsubscribe?event=_
|
||||
```
|
||||
|
||||
### tx
|
||||
|
||||
Returns a transaction matching the given transaction hash.
|
||||
|
||||
**Parameters**
|
||||
|
||||
1. hash - the transaction hash
|
||||
2. prove - include a proof of the transaction inclusion in the block in the result (optional, default: false)
|
||||
|
||||
**Returns**
|
||||
|
||||
- `proof`: the `types.TxProof` object
|
||||
- `tx`: `[]byte` - the transaction
|
||||
- `tx_result`: the `abci.Result` object
|
||||
- `index`: `int` - index of the transaction
|
||||
- `height`: `int` - height of the block where this transaction was in
|
||||
|
||||
**Example**
|
||||
|
||||
```bash
|
||||
curl -s 'http://localhost:46657/broadcast_tx_commit?tx="abc"' | jq .
|
||||
# {
|
||||
# "error": "",
|
||||
# "result": {
|
||||
# "hash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
# "log": "",
|
||||
# "data": "",
|
||||
# "code": 0
|
||||
# },
|
||||
# "id": "",
|
||||
# "jsonrpc": "2.0"
|
||||
# }
|
||||
|
||||
curl -s 'http://localhost:46657/tx?hash=0x2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF' | jq .
|
||||
# {
|
||||
# "error": "",
|
||||
# "result": {
|
||||
# "proof": {
|
||||
# "Proof": {
|
||||
# "aunts": []
|
||||
# },
|
||||
# "Data": "YWJjZA==",
|
||||
# "RootHash": "2B8EC32BA2579B3B8606E42C06DE2F7AFA2556EF",
|
||||
# "Total": 1,
|
||||
# "Index": 0
|
||||
# },
|
||||
# "tx": "YWJjZA==",
|
||||
# "tx_result": {
|
||||
# "log": "",
|
||||
# "data": "",
|
||||
# "code": 0
|
||||
# },
|
||||
# "index": 0,
|
||||
# "height": 52
|
||||
# },
|
||||
# "id": "",
|
||||
# "jsonrpc": "2.0"
|
||||
# }
|
||||
```
|
||||
|
||||
### More Examples
|
||||
|
||||
See the various bash tests using curl in `test/`, and examples using the `Go` API in `rpc/client/`.
|
||||
|
|
@ -1,33 +0,0 @@
|
|||
# Secure P2P
|
||||
|
||||
The Tendermint p2p protocol uses an authenticated encryption scheme based on the [Station-to-Station Protocol](https://en.wikipedia.org/wiki/Station-to-Station_protocol). The implementation uses [golang's](https://godoc.org/golang.org/x/crypto/nacl/box) [nacl box](http://nacl.cr.yp.to/box.html) for the actual authenticated encryption algorithm.
|
||||
|
||||
Each peer generates an ED25519 key-pair to use as a persistent (long-term) id.
|
||||
|
||||
When two peers establish a TCP connection, they first each generate an ephemeral ED25519 key-pair to use for this session, and send each other their respective ephemeral public keys. This happens in the clear.
|
||||
|
||||
They then each compute the shared secret. The shared secret is the multiplication of the peer's ephemeral private key by the other peer's ephemeral public key. The result is the same for both peers by the magic of [elliptic curves](https://en.wikipedia.org/wiki/Elliptic_curve_cryptography). The shared secret is used as the symmetric key for the encryption algorithm.
|
||||
|
||||
The two ephemeral public keys are sorted to establish a canonical order. Then a 24-byte nonce is generated by concatenating the public keys and hashing them with Ripemd160. Note Ripemd160 produces 20byte hashes, so the nonce ends with four 0s.
|
||||
|
||||
The nonce is used to seed the encryption - it is critical that the same nonce never be used twice with the same private key. For convenience, the last bit of the nonce is flipped, giving us two nonces: one for encrypting our own messages, one for decrypting our peer's. Which ever peer has the higher public key uses the "bit-flipped" nonce for encryption.
|
||||
|
||||
Now, a challenge is generated by concatenating the ephemeral public keys and taking the SHA256 hash.
|
||||
|
||||
Each peer signs the challenge with their persistent private key, and sends the other peer an AuthSigMsg, containing their persistent public key and the signature. On receiving an AuthSigMsg, the peer verifies the signature.
|
||||
|
||||
The peers are now authenticated.
|
||||
|
||||
All future communications can now be encrypted using the shared secret and the generated nonces, where each nonce is incremented by one each time it is used. The communications maintain Perfect Forward Secrecy, as the persistent key pair was not used for generating secrets - only for authenticating.
|
||||
|
||||
Caveat
|
||||
------
|
||||
This system is still vulnerable to a Man-In-The-Middle attack if the persistent public key of the remote node is not known in advance. The only way to mitigate this is with a public key authentication system, such as the Web-of-Trust or Certificate Authorities. In our case, we can use the blockchain itself as a certificate authority to ensure that we are connected to at least one validator.
|
||||
|
||||
Links
|
||||
------
|
||||
|
||||
- [Implementation](https://github.com/tendermint/go-p2p/blob/master/secret_connection.go#L49)
|
||||
- [Original STS paper by Whitfield Diffie, Paul C. van Oorschot and Michael J. Wiener](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.216.6107&rep=rep1&type=pdf)
|
||||
- [Further work on secret handshakes](https://dominictarr.github.io/secret-handshake-paper/shs.pdf)
|
||||
|
||||
|
|
@ -1,2 +0,0 @@
|
|||
# types
|
||||
see the [godoc version](https://godoc.org/github.com/tendermint/tendermint/types)
|
||||
|
|
@ -1,21 +0,0 @@
|
|||
# Validators
|
||||
|
||||
Validators are responsible for committing new blocks in the blockchain.
|
||||
These validators participate in the consensus protocol by broadcasting _votes_ which contain cryptographic signatures signed by each validator's public key.
|
||||
|
||||
Some Proof-of-Stake consensus algorithms aim to create a "completely" decentralized system where all stakeholders (even those who are not always available online) participate in the committing of blocks. Tendermint has a different approach to block creation. Validators are expected to be online, and the set of validators is permissioned/curated by some external process. Proof-of-stake is not required, but can be implemented on top of Tendermint consensus. That is, validators may be required to post collateral on-chain, off-chain, or may not be required to post any collateral at all.
|
||||
|
||||
Validators have a cryptographic key-pair and an associated amount of "voting power". Voting power need not be the same.
|
||||
|
||||
## Becoming a Validator
|
||||
|
||||
There are two ways to become validator.
|
||||
|
||||
1. They can be pre-established in the [genesis state](/docs/specs/genesis)
|
||||
2. The [ABCI app responds to the EndBlock message](https://github.com/tendermint/abci) with changes to the existing validator set.
|
||||
|
||||
## Committing a Block
|
||||
|
||||
_+2/3 is short for "more than 2/3"_
|
||||
|
||||
A block is committed when +2/3 of the validator set sign [precommit votes](/docs/specs/block-structure#vote) for that block at the same [round](/docs/specs/consensus). The +2/3 set of precommit votes is called a [_commit_](/docs/specs/block-structure#commit). While any +2/3 set of precommits for the same block at the same height&round can serve as validation, the canonical commit is included in the next block (see [LastCommit](/docs/specs/block-structure).
|
||||
|
|
@ -1,119 +0,0 @@
|
|||
# Wire Protocol
|
||||
|
||||
The [Tendermint wire protocol](https://github.com/tendermint/go-wire) encodes data in [c-style binary](#binary) and [JSON](#json) form.
|
||||
|
||||
## Supported types
|
||||
|
||||
- Primitive types
|
||||
- `uint8` (aka `byte`), `uint16`, `uint32`, `uint64`
|
||||
- `int8`, `int16`, `int32`, `int64`
|
||||
- `uint`, `int`: variable length (un)signed integers
|
||||
- `string`, `[]byte`
|
||||
- `time`
|
||||
- Derived types
|
||||
- structs
|
||||
- var-length arrays of a particular type
|
||||
- fixed-length arrays of a particular type
|
||||
- interfaces: registered union types preceded by a `type byte`
|
||||
- pointers
|
||||
|
||||
## Binary
|
||||
|
||||
**Fixed-length primitive types** are encoded with 1,2,3, or 4 big-endian bytes.
|
||||
- `uint8` (aka `byte`), `uint16`, `uint32`, `uint64`: takes 1,2,3, and 4 bytes respectively
|
||||
- `int8`, `int16`, `int32`, `int64`: takes 1,2,3, and 4 bytes respectively
|
||||
- `time`: `int64` representation of nanoseconds since epoch
|
||||
|
||||
**Variable-length integers** are encoded with a single leading byte representing the length of the following big-endian bytes. For signed negative integers, the most significant bit of the leading byte is a 1.
|
||||
|
||||
- `uint`: 1-byte length prefixed variable-size (0 ~ 255 bytes) unsigned integers
|
||||
- `int`: 1-byte length prefixed variable-size (0 ~ 127 bytes) signed integers
|
||||
|
||||
NOTE: While the number 0 (zero) is encoded with a single byte `x00`, the number 1 (one) takes two bytes to represent: `x0101`. This isn't the most efficient representation, but the rules are easier to remember.
|
||||
|
||||
| number | binary `uint` | binary `int` |
|
||||
| ------------ | ------------- | ------------- |
|
||||
| 0 | `x00` | `x00` |
|
||||
| 1 | `x0101` | `x0101` |
|
||||
| 2 | `x0102` | `x0102` |
|
||||
| 256 | `x020100` | `x020100` |
|
||||
| 2^(127*8)-1 | `x7FFFFF...` | `x7FFFFF...` |
|
||||
| 2^(127*8) | `x800100...` | overflow |
|
||||
| 2^(255*8)-1 | `xFFFFFF...` | overflow |
|
||||
| -1 | n/a | `x8101` |
|
||||
| -2 | n/a | `x8102` |
|
||||
| -256 | n/a | `x820100` |
|
||||
|
||||
**Structures** are encoded by encoding the field values in order of declaration.
|
||||
|
||||
```go
|
||||
type Foo struct {
|
||||
MyString string
|
||||
MyUint32 uint32
|
||||
}
|
||||
var foo = Foo{"626172", math.MaxUint32}
|
||||
|
||||
/* The binary representation of foo:
|
||||
0103626172FFFFFFFF
|
||||
0103: `int` encoded length of string, here 3
|
||||
626172: 3 bytes of string "bar"
|
||||
FFFFFFFF: 4 bytes of uint32 MaxUint32
|
||||
*/
|
||||
```
|
||||
|
||||
**Variable-length arrays** are encoded with a leading `int` denoting the length of the array followed by the binary representation of the items. **Fixed-length arrays** are similar but aren't preceded by the leading `int`.
|
||||
|
||||
```go
|
||||
foos := []Foo{foo, foo}
|
||||
|
||||
/* The binary representation of foos:
|
||||
01020103626172FFFFFFFF0103626172FFFFFFFF
|
||||
0102: `int` encoded length of array, here 2
|
||||
0103626172FFFFFFFF: the first `foo`
|
||||
0103626172FFFFFFFF: the second `foo`
|
||||
*/
|
||||
|
||||
foos := [2]Foo{foo, foo} // fixed-length array
|
||||
|
||||
/* The binary representation of foos:
|
||||
0103626172FFFFFFFF0103626172FFFFFFFF
|
||||
0103626172FFFFFFFF: the first `foo`
|
||||
0103626172FFFFFFFF: the second `foo`
|
||||
*/
|
||||
```
|
||||
|
||||
**Interfaces** can represent one of any number of concrete types. The concrete types of an interface must first be declared with their corresponding `type byte`. An interface is then encoded with the leading `type byte`, then the binary encoding of the underlying concrete type.
|
||||
|
||||
NOTE: The byte `x00` is reserved for the `nil` interface value and `nil` pointer values.
|
||||
|
||||
```go
|
||||
type Animal interface{}
|
||||
type Dog uint32
|
||||
type Cat string
|
||||
|
||||
RegisterInterface(
|
||||
struct{ Animal }{}, // Convenience for referencing the 'Animal' interface
|
||||
ConcreteType{Dog(0), 0x01}, // Register the byte 0x01 to denote a Dog
|
||||
ConcreteType{Cat(""), 0x02}, // Register the byte 0x02 to denote a Cat
|
||||
)
|
||||
|
||||
var animal Animal = Dog(02)
|
||||
|
||||
/* The binary representation of animal:
|
||||
010102
|
||||
01: the type byte for a `Dog`
|
||||
0102: the bytes of Dog(02)
|
||||
*/
|
||||
```
|
||||
|
||||
**Pointers** are encoded with a single leading byte `x00` for `nil` pointers, otherwise encoded with a leading byte `x01` followed by the binary encoding of the value pointed to.
|
||||
|
||||
NOTE: It's easy to convert pointer types into interface types, since the `type byte` `x00` is always `nil`.
|
||||
|
||||
## JSON
|
||||
|
||||
The JSON codec is compatible with the [`binary`](#binary) codec, and is fairly intuitive if you're already familiar with golang's JSON encoding. Some quirks are noted below:
|
||||
|
||||
- variable-length and fixed-length bytes are encoded as uppercase hexadecimal strings
|
||||
- interface values are encoded as an array of two items: `[type_byte, concrete_value]`
|
||||
- times are encoded as rfc2822 strings
|
||||
|
|
@ -0,0 +1,44 @@
|
|||
Validators
|
||||
==========
|
||||
|
||||
Validators are responsible for committing new blocks in the blockchain.
|
||||
These validators participate in the consensus protocol by broadcasting
|
||||
*votes* which contain cryptographic signatures signed by each
|
||||
validator's public key.
|
||||
|
||||
Some Proof-of-Stake consensus algorithms aim to create a "completely"
|
||||
decentralized system where all stakeholders (even those who are not
|
||||
always available online) participate in the committing of blocks.
|
||||
Tendermint has a different approach to block creation. Validators are
|
||||
expected to be online, and the set of validators is permissioned/curated
|
||||
by some external process. Proof-of-stake is not required, but can be
|
||||
implemented on top of Tendermint consensus. That is, validators may be
|
||||
required to post collateral on-chain, off-chain, or may not be required
|
||||
to post any collateral at all.
|
||||
|
||||
Validators have a cryptographic key-pair and an associated amount of
|
||||
"voting power". Voting power need not be the same.
|
||||
|
||||
Becoming a Validator
|
||||
--------------------
|
||||
|
||||
There are two ways to become validator.
|
||||
|
||||
1. They can be pre-established in the `genesis
|
||||
state </docs/specs/genesis>`__
|
||||
2. The `ABCI app responds to the EndBlock
|
||||
message <https://github.com/tendermint/abci>`__ with changes to the
|
||||
existing validator set.
|
||||
|
||||
Committing a Block
|
||||
------------------
|
||||
|
||||
*+2/3 is short for "more than 2/3"*
|
||||
|
||||
A block is committed when +2/3 of the validator set sign `precommit
|
||||
votes </docs/specs/block-structure#vote>`__ for that block at the same
|
||||
`round </docs/specs/consensus>`__. The +2/3 set of precommit votes is
|
||||
called a `*commit* </docs/specs/block-structure#commit>`__. While any
|
||||
+2/3 set of precommits for the same block at the same height&round can
|
||||
serve as validation, the canonical commit is included in the next block
|
||||
(see `LastCommit </docs/specs/block-structure>`__.
|
||||
|
|
@ -0,0 +1,172 @@
|
|||
Wire Protocol
|
||||
=============
|
||||
|
||||
The `Tendermint wire protocol <https://github.com/tendermint/go-wire>`__
|
||||
encodes data in `c-style binary <#binary>`__ and `JSON <#json>`__ form.
|
||||
|
||||
Supported types
|
||||
---------------
|
||||
|
||||
- Primitive types
|
||||
- ``uint8`` (aka ``byte``), ``uint16``, ``uint32``, ``uint64``
|
||||
- ``int8``, ``int16``, ``int32``, ``int64``
|
||||
- ``uint``, ``int``: variable length (un)signed integers
|
||||
- ``string``, ``[]byte``
|
||||
- ``time``
|
||||
- Derived types
|
||||
- structs
|
||||
- var-length arrays of a particular type
|
||||
- fixed-length arrays of a particular type
|
||||
- interfaces: registered union types preceded by a ``type byte``
|
||||
- pointers
|
||||
|
||||
Binary
|
||||
------
|
||||
|
||||
**Fixed-length primitive types** are encoded with 1,2,3, or 4 big-endian
|
||||
bytes. - ``uint8`` (aka ``byte``), ``uint16``, ``uint32``, ``uint64``:
|
||||
takes 1,2,3, and 4 bytes respectively - ``int8``, ``int16``, ``int32``,
|
||||
``int64``: takes 1,2,3, and 4 bytes respectively - ``time``: ``int64``
|
||||
representation of nanoseconds since epoch
|
||||
|
||||
**Variable-length integers** are encoded with a single leading byte
|
||||
representing the length of the following big-endian bytes. For signed
|
||||
negative integers, the most significant bit of the leading byte is a 1.
|
||||
|
||||
- ``uint``: 1-byte length prefixed variable-size (0 ~ 255 bytes)
|
||||
unsigned integers
|
||||
- ``int``: 1-byte length prefixed variable-size (0 ~ 127 bytes) signed
|
||||
integers
|
||||
|
||||
NOTE: While the number 0 (zero) is encoded with a single byte ``x00``,
|
||||
the number 1 (one) takes two bytes to represent: ``x0101``. This isn't
|
||||
the most efficient representation, but the rules are easier to remember.
|
||||
|
||||
+---------------+----------------+----------------+
|
||||
| number | binary | binary ``int`` |
|
||||
| | ``uint`` | |
|
||||
+===============+================+================+
|
||||
| 0 | ``x00`` | ``x00`` |
|
||||
+---------------+----------------+----------------+
|
||||
| 1 | ``x0101`` | ``x0101`` |
|
||||
+---------------+----------------+----------------+
|
||||
| 2 | ``x0102`` | ``x0102`` |
|
||||
+---------------+----------------+----------------+
|
||||
| 256 | ``x020100`` | ``x020100`` |
|
||||
+---------------+----------------+----------------+
|
||||
| 2^(127\ *8)-1 | ``x800100...`` | overflow |
|
||||
| \| | | |
|
||||
| ``x7FFFFF...` | | |
|
||||
| ` | | |
|
||||
| \| | | |
|
||||
| ``x7FFFFF...` | | |
|
||||
| ` | | |
|
||||
| \| \| | | |
|
||||
| 2^(127*\ 8) | | |
|
||||
+---------------+----------------+----------------+
|
||||
| 2^(255\*8)-1 |
|
||||
| \| |
|
||||
| ``xFFFFFF...` |
|
||||
| ` |
|
||||
| \| overflow |
|
||||
| \| \| -1 \| |
|
||||
| n/a \| |
|
||||
| ``x8101`` \| |
|
||||
| \| -2 \| n/a |
|
||||
| \| ``x8102`` |
|
||||
| \| \| -256 \| |
|
||||
| n/a \| |
|
||||
| ``x820100`` |
|
||||
| \| |
|
||||
+---------------+----------------+----------------+
|
||||
|
||||
**Structures** are encoded by encoding the field values in order of
|
||||
declaration.
|
||||
|
||||
.. code:: go
|
||||
|
||||
type Foo struct {
|
||||
MyString string
|
||||
MyUint32 uint32
|
||||
}
|
||||
var foo = Foo{"626172", math.MaxUint32}
|
||||
|
||||
/* The binary representation of foo:
|
||||
0103626172FFFFFFFF
|
||||
0103: `int` encoded length of string, here 3
|
||||
626172: 3 bytes of string "bar"
|
||||
FFFFFFFF: 4 bytes of uint32 MaxUint32
|
||||
*/
|
||||
|
||||
**Variable-length arrays** are encoded with a leading ``int`` denoting
|
||||
the length of the array followed by the binary representation of the
|
||||
items. **Fixed-length arrays** are similar but aren't preceded by the
|
||||
leading ``int``.
|
||||
|
||||
.. code:: go
|
||||
|
||||
foos := []Foo{foo, foo}
|
||||
|
||||
/* The binary representation of foos:
|
||||
01020103626172FFFFFFFF0103626172FFFFFFFF
|
||||
0102: `int` encoded length of array, here 2
|
||||
0103626172FFFFFFFF: the first `foo`
|
||||
0103626172FFFFFFFF: the second `foo`
|
||||
*/
|
||||
|
||||
foos := [2]Foo{foo, foo} // fixed-length array
|
||||
|
||||
/* The binary representation of foos:
|
||||
0103626172FFFFFFFF0103626172FFFFFFFF
|
||||
0103626172FFFFFFFF: the first `foo`
|
||||
0103626172FFFFFFFF: the second `foo`
|
||||
*/
|
||||
|
||||
**Interfaces** can represent one of any number of concrete types. The
|
||||
concrete types of an interface must first be declared with their
|
||||
corresponding ``type byte``. An interface is then encoded with the
|
||||
leading ``type byte``, then the binary encoding of the underlying
|
||||
concrete type.
|
||||
|
||||
NOTE: The byte ``x00`` is reserved for the ``nil`` interface value and
|
||||
``nil`` pointer values.
|
||||
|
||||
.. code:: go
|
||||
|
||||
type Animal interface{}
|
||||
type Dog uint32
|
||||
type Cat string
|
||||
|
||||
RegisterInterface(
|
||||
struct{ Animal }{}, // Convenience for referencing the 'Animal' interface
|
||||
ConcreteType{Dog(0), 0x01}, // Register the byte 0x01 to denote a Dog
|
||||
ConcreteType{Cat(""), 0x02}, // Register the byte 0x02 to denote a Cat
|
||||
)
|
||||
|
||||
var animal Animal = Dog(02)
|
||||
|
||||
/* The binary representation of animal:
|
||||
010102
|
||||
01: the type byte for a `Dog`
|
||||
0102: the bytes of Dog(02)
|
||||
*/
|
||||
|
||||
**Pointers** are encoded with a single leading byte ``x00`` for ``nil``
|
||||
pointers, otherwise encoded with a leading byte ``x01`` followed by the
|
||||
binary encoding of the value pointed to.
|
||||
|
||||
NOTE: It's easy to convert pointer types into interface types, since the
|
||||
``type byte`` ``x00`` is always ``nil``.
|
||||
|
||||
JSON
|
||||
----
|
||||
|
||||
The JSON codec is compatible with the ```binary`` <#binary>`__ codec,
|
||||
and is fairly intuitive if you're already familiar with golang's JSON
|
||||
encoding. Some quirks are noted below:
|
||||
|
||||
- variable-length and fixed-length bytes are encoded as uppercase
|
||||
hexadecimal strings
|
||||
- interface values are encoded as an array of two items:
|
||||
``[type_byte, concrete_value]``
|
||||
- times are encoded as rfc2822 strings
|
||||
Loading…
Reference in New Issue