Merge pull request #1263 from cosmos/bucky/staking-spec-updates

spec updates

docs/spec/README.md

@@ -5,15 +5,14 @@ the Cosmos Hub.
 
 NOTE: the specifications are not yet complete and very much a work in progress.
 
-- [Basecoin](basecoin) - Cosmos SDK related specifications and transactions for
-  sending tokens.
-- [Governance](governance) - Governance related specifications including 
-  proposals and voting.
-- [IBC](ibc) - Specification of the Cosmos inter-blockchain communication (IBC) protocol.
-- [Staking](staking) - Proof-of-stake related specifications including bonding 
-  and delegation transactions, inflation, etc.
-- [Slashing](slashing) - Specifications of validator punishment mechanisms
-- [Provisioning](provisioning) - Fee distribution, and atom provision distribution specification
+- [Store](store) - The core Merkle store that holds the state.
+- [Auth](auth) - The structure and authnentication of accounts and transactions.
+- [Bank](bank) - Sending tokens.
+- [Governance](governance) - Proposals and voting.
+- [IBC](ibc) - Inter-Blockchain Communication (IBC) protocol.
+- [Staking](staking) - Proof-of-stake bonding, delegation, etc.
+- [Slashing](slashing) - Validator punishment mechanisms.
+- [Provisioning](provisioning) - Fee distribution, and atom provision distribution 
 - [Other](other) - Other components of the Cosmos Hub, including the reserve 
   pool, All in Bits vesting, etc.
 

docs/spec/WIP_slashing/valset-changes.md

@@ -1,100 +0,0 @@
-# Validator Set Changes
-
-## Slashing
-
-Messges which may compromise the safety of the underlying consensus protocol ("equivocations")
-result in some amount of the offending validator's shares being removed ("slashed").
-
-Currently, such messages include only the following:
-
-- prevotes by the same validator for more than one BlockID at the same
-  Height and Round 
-- precommits by the same validator for more than one BlockID at the same
-  Height and Round 
-
-We call any such pair of conflicting votes `Evidence`. Full nodes in the network prioritize the 
-detection and gossipping of `Evidence` so that it may be rapidly included in blocks and the offending
-validators punished.
-
-For some `evidence` to be valid, it must satisfy: 
-
-`evidence.Timestamp >= block.Timestamp - MAX_EVIDENCE_AGE`
-
-where `evidence.Timestamp` is the timestamp in the block at height
-`evidence.Height` and `block.Timestamp` is the current block timestamp.
-
-If valid evidence is included in a block, the offending validator loses
-a constant `SLASH_PROPORTION` of their current stake at the beginning of the block:
-
-```
-oldShares = validator.shares
-validator.shares = oldShares * (1 - SLASH_PROPORTION)
-```
-
-This ensures that offending validators are punished the same amount whether they
-act as a single validator with X stake or as N validators with collectively X
-stake.
-
-
-## Automatic Unbonding
-
-Every block includes a set of precommits by the validators for the previous block, 
-known as the LastCommit. A LastCommit is valid so long as it contains precommits from +2/3 of voting power.
-
-Proposers are incentivized to include precommits from all
-validators in the LastCommit by receiving additional fees
-proportional to the difference between the voting power included in the
-LastCommit and +2/3 (see [TODO](https://github.com/cosmos/cosmos-sdk/issues/967)).
-
-Validators are penalized for failing to be included in the LastCommit for some
-number of blocks by being automatically unbonded.
-
-The following information is stored with each validator candidate, and is only non-zero if the candidate becomes an active validator:
-
-```go
-type ValidatorSigningInfo struct {
-  StartHeight           int64
-  IndexOffset           int64
-  JailedUntil           int64
-  SignedBlocksCounter   int64
-  SignedBlocksBitArray  BitArray
-}
-```
-
-Where:
-* `StartHeight` is set to the height that the candidate became an active validator (with non-zero voting power).
-* `IndexOffset` is incremented each time the candidate was a bonded validator in a block (and may have signed a precommit or not).
-* `JailedUntil` is set whenever the candidate is revoked due to downtime
-* `SignedBlocksCounter` is a counter kept to avoid unnecessary array reads. `SignedBlocksBitArray.Sum() == SignedBlocksCounter` always.
-* `SignedBlocksBitArray` is a bit-array of size `SIGNED_BLOCKS_WINDOW` that records, for each of the last `SIGNED_BLOCKS_WINDOW` blocks,
-whether or not this validator was included in the LastCommit. It uses a `1` if the validator was included, and a `0` if it was not. Note it is initialized with all 0s.
-
-At the beginning of each block, we update the signing info for each validator and check if they should be automatically unbonded:
-
-```
-height := block.Height
-
-for val in block.Validators:
-  signInfo = val.SignInfo
-  index := signInfo.IndexOffset % SIGNED_BLOCKS_WINDOW
-  signInfo.IndexOffset++
-  previous = signInfo.SignedBlocksBitArray.Get(index)
-
-  // update counter if array has changed
-  if previous and val in block.AbsentValidators:
-    signInfo.SignedBlocksBitArray.Set(index, 0)
-    signInfo.SignedBlocksCounter--
-  else if !previous and val not in block.AbsentValidators:
-    signInfo.SignedBlocksBitArray.Set(index, 1)
-    signInfo.SignedBlocksCounter++
-  // else previous == val not in block.AbsentValidators, no change
-
-  // validator must be active for at least SIGNED_BLOCKS_WINDOW
-  // before they can be automatically unbonded for failing to be 
-  // included in 50% of the recent LastCommits
-  minHeight = signInfo.StartHeight + SIGNED_BLOCKS_WINDOW
-  minSigned = SIGNED_BLOCKS_WINDOW / 2
-  if height > minHeight AND signInfo.SignedBlocksCounter < minSigned:
-    signInfo.JailedUntil = block.Time + DOWNTIME_UNBOND_DURATION
-    slash & unbond the validator
-```

docs/spec/slashing/end_block.md

@@ -0,0 +1,102 @@
+# End-Block 
+
+## Slashing
+
+Tendermint blocks can include
+[Evidence](https://github.com/tendermint/tendermint/blob/develop/docs/spec/blockchain/blockchain.md#evidence), which indicates that a validator
+committed malicious behaviour. The relevant information is forwarded to the
+application as [ABCI
+Evidence](https://github.com/tendermint/abci/blob/develop/types/types.proto#L259), so the validator an be accordingly punished.
+
+For some `evidence` to be valid, it must satisfy: 
+
+`evidence.Timestamp >= block.Timestamp - MAX_EVIDENCE_AGE`
+
+where `evidence.Timestamp` is the timestamp in the block at height
+`evidence.Height` and `block.Timestamp` is the current block timestamp.
+
+If valid evidence is included in a block, the validator's stake is reduced by `SLASH_PROPORTION` of 
+what their stake was when the equivocation occurred (rather than when the evidence was discovered):
+
+```
+curVal := validator
+oldVal := loadValidator(evidence.Height, evidence.Address)
+
+slashAmount := SLASH_PROPORTION * oldVal.Shares
+
+curVal.Shares = max(0, curVal.Shares - slashAmount)
+```
+
+This ensures that offending validators are punished the same amount whether they
+act as a single validator with X stake or as N validators with collectively X
+stake.
+
+We also need to loop through the unbondings and redelegations to slash them as
+well:
+
+```
+unbondings := getUnbondings(validator.Address)
+for unbond in unbondings {
+    if was not bonded before evidence.Height {
+        continue
+    }
+    unbond.InitialTokens
+    burn := unbond.InitialTokens * SLASH_PROPORTION
+    unbond.Tokens = max(0, unbond.Tokens - burn)
+}
+
+// only care if source gets slashed because we're already bonded to destination
+// so if destination validator gets slashed our delegation just has same shares
+// of smaller pool.
+redels := getRedelegationsBySource(validator.Address)
+for redel in redels {
+
+    if was not bonded before evidence.Height {
+        continue
+    }
+
+    burn := redel.InitialTokens * SLASH_PROPORTION
+
+    amount := unbondFromValidator(redel.Destination, burn)
+    destroy(amount)
+}
+```
+
+## Automatic Unbonding
+
+At the beginning of each block, we update the signing info for each validator and check if they should be automatically unbonded:
+
+```
+height := block.Height
+
+for val in block.Validators:
+  signInfo = SigningInfo.Get(val.Address)
+  if signInfo == nil{
+        signInfo.StartHeight = height
+  }
+
+  index := signInfo.IndexOffset % SIGNED_BLOCKS_WINDOW
+  signInfo.IndexOffset++
+  previous = SigningBitArray.Get(val.Address, index)
+
+  // update counter if array has changed
+  if previous and val in block.AbsentValidators:
+    SigningBitArray.Set(val.Address, index, false)
+    signInfo.SignedBlocksCounter--
+  else if !previous and val not in block.AbsentValidators:
+    SigningBitArray.Set(val.Address, index, true)
+    signInfo.SignedBlocksCounter++
+  // else previous == val not in block.AbsentValidators, no change
+
+  // validator must be active for at least SIGNED_BLOCKS_WINDOW
+  // before they can be automatically unbonded for failing to be 
+  // included in 50% of the recent LastCommits
+  minHeight = signInfo.StartHeight + SIGNED_BLOCKS_WINDOW
+  minSigned = SIGNED_BLOCKS_WINDOW / 2
+  if height > minHeight AND signInfo.SignedBlocksCounter < minSigned:
+    signInfo.JailedUntil = block.Time + DOWNTIME_UNBOND_DURATION
+
+    slash & unbond the validator
+
+  SigningInfo.Set(val.Address, signInfo)
+```

docs/spec/slashing/state.md

@@ -0,0 +1,51 @@
+## State
+
+### Signing Info
+
+Every block includes a set of precommits by the validators for the previous block, 
+known as the LastCommit. A LastCommit is valid so long as it contains precommits from +2/3 of voting power.
+
+Proposers are incentivized to include precommits from all
+validators in the LastCommit by receiving additional fees
+proportional to the difference between the voting power included in the
+LastCommit and +2/3 (see [TODO](https://github.com/cosmos/cosmos-sdk/issues/967)).
+
+Validators are penalized for failing to be included in the LastCommit for some
+number of blocks by being automatically unbonded.
+
+Information about validator activity is tracked in a `ValidatorSigningInfo`. 
+It is indexed in the store as follows:
+
+- SigningInfo: ` 0x01 | ValTendermintAddr -> amino(valSigningInfo)`
+- SigningBitArray: ` 0x02 | ValTendermintAddr | LittleEndianUint64(signArrayIndex) -> VarInt(didSign)`
+
+The first map allows us to easily lookup the recent signing info for a
+validator, according to the Tendermint validator address. The second map acts as
+a bit-array of size `SIGNED_BLOCKS_WINDOW` that tells us if the validator signed for a given index in the bit-array.
+
+The index in the bit-array is given as little endian uint64.
+
+The result is a `varint` that takes on `0` or `1`, where `0` indicates the
+validator did not sign the corresponding block, and `1` indicates they did.
+
+Note that the SigningBitArray is not explicitly initialized up-front. Keys are
+added as we progress through the first `SIGNED_BLOCKS_WINDOW` blocks for a newly
+bonded validator.
+
+The information stored for tracking validator liveness is as follows:
+
+```go
+type ValidatorSigningInfo struct {
+  StartHeight           int64
+  IndexOffset           int64
+  JailedUntil           int64
+  SignedBlocksCounter   int64
+}
+
+```
+
+Where:
+* `StartHeight` is set to the height that the candidate became an active validator (with non-zero voting power).
+* `IndexOffset` is incremented each time the candidate was a bonded validator in a block (and may have signed a precommit or not).
+* `JailedUntil` is set whenever the candidate is revoked due to downtime
+* `SignedBlocksCounter` is a counter kept to avoid unnecessary array reads. `SignedBlocksBitArray.Sum() == SignedBlocksCounter` always.

docs/spec/staking/state.md

@@ -1,44 +1,43 @@
 ## State
 
 ### Pool
- - index: n/a single-record
+
+ - key: `01`
+ - value: `amino(pool)`
 
 The pool is a space for all dynamic global state of the Cosmos Hub.  It tracks
 information about the total amounts of Atoms in all states, representative
 validator shares for stake in the global pools, moving Atom inflation
 information, etc.
 
- - stored object:
-
 ```golang
 type Pool struct {
     LooseUnbondedTokens int64   // tokens not associated with any validator
-	UnbondedTokens      int64   // reserve of unbonded tokens held with validators
-	UnbondingTokens     int64   // tokens moving from bonded to unbonded pool
-	BondedTokens        int64   // reserve of bonded tokens
-	UnbondedShares      sdk.Rat // sum of all shares distributed for the Unbonded Pool
-	UnbondingShares     sdk.Rat // shares moving from Bonded to Unbonded Pool
-	BondedShares        sdk.Rat // sum of all shares distributed for the Bonded Pool
-	InflationLastTime   int64   // block which the last inflation was processed // TODO make time
-	Inflation           sdk.Rat // current annual inflation rate
-
-	DateLastCommissionReset int64  // unix timestamp for last commission accounting reset (daily)
+    UnbondedTokens      int64   // reserve of unbonded tokens held with validators
+    UnbondingTokens     int64   // tokens moving from bonded to unbonded pool
+    BondedTokens        int64   // reserve of bonded tokens
+    UnbondedShares      sdk.Rat // sum of all shares distributed for the Unbonded Pool
+    UnbondingShares     sdk.Rat // shares moving from Bonded to Unbonded Pool
+    BondedShares        sdk.Rat // sum of all shares distributed for the Bonded Pool
+    InflationLastTime   int64   // block which the last inflation was processed // TODO make time
+    Inflation           sdk.Rat // current annual inflation rate
+    
+    DateLastCommissionReset int64  // unix timestamp for last commission accounting reset (daily)
 }
 
 type PoolShares struct {
-	Status sdk.BondStatus // either: unbonded, unbonding, or bonded
-	Amount sdk.Rat        // total shares of type ShareKind
+    Status sdk.BondStatus // either: unbonded, unbonding, or bonded
+    Amount sdk.Rat        // total shares of type ShareKind
 }
 ```
 
 ### Params
- - index: n/a single-record
+ - key: `00`
+ - value: `amino(params)`
 
 Params is global data structure that stores system parameters and defines
 overall functioning of the stake module. 
 
- - stored object:
-
 ```golang
 type Params struct {
     InflationRateChange sdk.Rat // maximum annual change in inflation rate
@@ -52,40 +51,64 @@ type Params struct {
 ```
 
 ### Validator
- - index 1: validator owner address
- - index 2: validator Tendermint PubKey
- - index 3: bonded validators only
- - index 4: voting power
 
-Related Store which holds Validator.ABCIValidator()
- - index: validator owner address
+Validators are identified according to the `ValOwnerAddr`, 
+an SDK account address for the owner of the validator.
+
+Validators also have a `ValTendermintAddr`, the address 
+of the public key of the validator.
+
+Validators are indexed in the store using the following maps:
+
+ - Validators: `0x02 | ValOwnerAddr -> amino(validator)`
+ - ValidatorsByPubKey: `0x03 | ValTendermintAddr -> ValOwnerAddr`
+ - ValidatorsByPower: `0x05 | power | blockHeight | blockTx  -> ValOwnerAddr`
+
+ `Validators` is the primary index - it ensures that each owner can have only one
+ associated validator, where the public key of that validator can change in the
+ future. Delegators can refer to the immutable owner of the validator, without
+ concern for the changing public key.
+
+ `ValidatorsByPubKey` is a secondary index that enables lookups for slashing.
+ When Tendermint reports evidence, it provides the validator address, so this
+ map is needed to find the owner.
+
+ `ValidatorsByPower` is a secondary index that provides a sorted list of
+ potential validators to quickly determine the current active set. For instance,
+ the first 100 validators in this list can be returned with every EndBlock.
 
 The `Validator` holds the current state and some historical actions of the
 validator.
 
- - stored object:
-
 ```golang
 type Validator struct {
-	Owner           sdk.Address    // sender of BondTx - UnbondTx returns here
-	ConsensusPubKey crypto.PubKey  // Tendermint consensus pubkey of validator
-	Revoked         bool           // has the validator been revoked?
+    ConsensusPubKey crypto.PubKey  // Tendermint consensus pubkey of validator
+    Revoked         bool           // has the validator been revoked?
+    
+    PoolShares      PoolShares     // total shares for tokens held in the pool
+    DelegatorShares sdk.Rat        // total shares issued to a validator's delegators
+    SlashRatio      sdk.Rat        // increases each time the validator is slashed
+    
+    Description        Description  // description terms for the validator
+    
+    // Needed for ordering vals in the bypower key
+    BondHeight         int64        // earliest height as a bonded validator
+    BondIntraTxCounter int16        // block-local tx index of validator change
+    
+    CommissionInfo      CommissionInfo // info about the validator's commission
+    
+    ProposerRewardPool sdk.Coins    // reward pool collected from being the proposer
+    
+    // TODO: maybe this belongs in distribution module ?
+    PrevPoolShares PoolShares  // total shares of a global hold pools
+}
 
-	PoolShares      PoolShares     // total shares for tokens held in the pool
-	DelegatorShares sdk.Rat        // total shares issued to a validator's delegators
-	SlashRatio      sdk.Rat        // increases each time the validator is slashed
-
-	Description        Description // description terms for the validator
-	BondHeight         int64       // earliest height as a bonded validator
-	BondIntraTxCounter int16       // block-local tx index of validator change
-	ProposerRewardPool sdk.Coins   // reward pool collected from being the proposer
-
-	Commission            sdk.Rat  // the commission rate of fees charged to any delegators
-	CommissionMax         sdk.Rat  // maximum commission rate which this validator can ever charge
-	CommissionChangeRate  sdk.Rat  // maximum daily increase of the validator commission
-	CommissionChangeToday sdk.Rat  // commission rate change today, reset each day (UTC time)
-
-	PrevPoolShares PoolShares      // total shares of a global hold pools
+type CommissionInfo struct {
+    Rate        sdk.Rat  // the commission rate of fees charged to any delegators
+    Max         sdk.Rat  // maximum commission rate which this validator can ever charge
+    ChangeRate  sdk.Rat  // maximum daily increase of the validator commission
+    ChangeToday sdk.Rat  // commission rate change today, reset each day (UTC time)
+    LastChange  int64    // unix timestamp of last commission change
 }
 
 type Description struct {
@@ -97,47 +120,71 @@ type Description struct {
 ```
 
 ### Delegation
- - index: delegation address
+
+Delegations are identified by combining `DelegatorAddr` (the address of the delegator) with the ValOwnerAddr 
+Delegators are indexed in the store as follows:
+
+ - Delegation: ` 0x0A | DelegatorAddr | ValOwnerAddr -> amino(delegation)`
 
 Atom holders may delegate coins to validators; under this circumstance their
 funds are held in a `Delegation` data structure. It is owned by one 
 delegator, and is associated with the shares for one validator. The sender of 
 the transaction is the owner of the bond.
 
- - stored object:
-
 ```golang
 type Delegation struct {
-	DelegatorAddr sdk.Address // delegation owner address
-	ValidatorAddr sdk.Address // validator owner address
-	Shares        sdk.Rat     // delegation shares recieved 
-	Height        int64       // last height bond updated
+	Shares        sdk.Rat      // delegation shares recieved 
+	Height        int64        // last height bond updated
 }
 ```
 
 ### UnbondingDelegation
- - index: delegation address
+
+Shares in a `Delegation` can be unbonded, but they must for some time exist as an `UnbondingDelegation`,
+where shares can be reduced if Byzantine behaviour is detected.
+
+`UnbondingDelegation` are indexed in the store as:
+
+ - UnbondingDelegationByDelegator: ` 0x0B | DelegatorAddr | ValOwnerAddr ->
+   amino(unbondingDelegation)`
+ - UnbondingDelegationByValOwner: ` 0x0C | ValOwnerAddr | DelegatorAddr | ValOwnerAddr ->
+   nil`
+
+ The first map here is used in queries, to lookup all unbonding delegations for
+ a given delegator, while the second map is used in slashing, to lookup all
+ unbonding delegations associated with a given validator that need to be
+ slashed.
 
 A UnbondingDelegation object is created every time an unbonding is initiated.
 The unbond must be completed with a second transaction provided by the
 delegation owner after the unbonding period has passed.
 
- - stored object:
-
 ```golang
 type UnbondingDelegation struct {
-    DelegationKey    sdk.Address // key of the delegation
-    ExpectedTokens   sdk.Coins   // the value in Atoms of the amount of shares which are unbonding
-    StartSlashRatio  sdk.Rat     // validator slash ratio at unbonding initiation
+    Tokens           sdk.Coins   // the value in Atoms of the amount of shares which are unbonding
     CompleteTime     int64       // unix time to complete redelegation
-    CompleteHeight   int64       // block height to complete redelegation
 }
 ``` 
 
 ### Redelegation
- - index 1: delegation address
- - index 2: source validator owner address
- - index 3: destination validator owner address
+
+Shares in a `Delegation` can be rebonded to a different validator, but they must for some time exist as a `Redelegation`,
+where shares can be reduced if Byzantine behaviour is detected. This is tracked
+as moving a delegation from a `FromValOwnerAddr` to a `ToValOwnerAddr`.
+
+`Redelegation` are indexed in the store as:
+
+ - Redelegations: `0x0D | DelegatorAddr | FromValOwnerAddr | ToValOwnerAddr ->
+   amino(redelegation)`
+ - RedelegationsBySrc: `0x0E | FromValOwnerAddr | ToValOwnerAddr |
+   DelegatorAddr -> nil`
+ - RedelegationsByDst: `0x0F | ToValOwnerAddr | FromValOwnerAddr | DelegatorAddr
+   -> nil`
+
+
+The first map here is used for queries, to lookup all redelegations for a given
+delegator. The second map is used for slashing based on the FromValOwnerAddr,
+while the third map is for slashing based on the ToValOwnerAddr.
 
 A redelegation object is created every time a redelegation occurs. The
 redelegation must be completed with a second transaction provided by the
@@ -145,16 +192,10 @@ delegation owner after the unbonding period has passed.  The destination
 delegation of a redelegation may not itself undergo a new redelegation until
 the original redelegation has been completed.
 
- - stored object:
-
 ```golang
 type Redelegation struct {
-    SourceDelegation       sdk.Address // source delegation key
-    DestinationDelegation  sdk.Address // destination delegation key
     SourceShares           sdk.Rat     // amount of source shares redelegating
     DestinationShares      sdk.Rat     // amount of destination shares created at redelegation
-    SourceStartSlashRatio  sdk.Rat     // source validator slash ratio at unbonding initiation
     CompleteTime           int64       // unix time to complete redelegation
-    CompleteHeight         int64       // block height to complete redelegation
 }
 ```