mirror of https://github.com/poanetwork/hbbft.git
650 lines
26 KiB
Rust
650 lines
26 KiB
Rust
//! A _synchronous_ algorithm for dealerless distributed key generation.
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//!
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//! This protocol is meant to run in a _completely synchronous_ setting where each node handles all
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//! messages in the same order. It can e.g. exchange messages as transactions on top of
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//! `HoneyBadger`, or it can run "on-chain", i.e. committing its messages to a blockchain.
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//!
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//! Its messages are encrypted where necessary, so they can be publicly broadcast.
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//!
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//! When the protocol completes, every node receives a secret key share suitable for threshold
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//! signatures and encryption. The secret master key is not known by anyone. The protocol succeeds
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//! if up to _t_ nodes are faulty, where _t_ is the `threshold` parameter. The number of nodes must
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//! be at least _2 t + 1_.
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//!
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//! ## Usage
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//!
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//! Before beginning the threshold key generation process, each validator needs to generate a
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//! regular (non-threshold) key pair and multicast its public key. `SyncKeyGen::new` returns the
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//! instance itself and a `Part` message, containing a contribution to the new threshold keys.
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//! It needs to be sent to all nodes. `SyncKeyGen::handle_part` in turn produces an `Ack`
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//! message, which is also multicast.
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//!
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//! All nodes must handle the exact same set of `Part` and `Ack` messages. In this sense the
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//! algorithm is synchronous: If Alice's `Ack` was handled by Bob but not by Carol, Bob and
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//! Carol could receive different public key sets, and secret key shares that don't match. One way
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//! to ensure this is to commit the messages to a public ledger before handling them, e.g. by
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//! feeding them to a preexisting instance of Honey Badger. The messages will then appear in the
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//! same order for everyone.
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//!
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//! To complete the process, call `SyncKeyGen::generate`. It produces your secret key share and the
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//! public key set.
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//!
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//! While not asynchronous, the algorithm is fault tolerant: It is not necessary to handle a
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//! `Part` and all `Ack` messages from every validator. A `Part` is _complete_ if it
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//! received at least _2 t + 1_ valid `Ack`s. Only complete `Part`s are used for key
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//! generation in the end, and as long as at least one complete `Part` is from a correct node,
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//! the new key set is secure. You can use `SyncKeyGen::is_ready` to check whether at least
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//! _t + 1_ `Part`s are complete. So all nodes can call `generate` as soon as `is_ready` returns
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//! `true`.
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//!
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//! Alternatively, you can use any stronger criterion, too, as long as all validators call
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//! `generate` at the same point, i.e. after handling the same set of messages.
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//! `SyncKeyGen::count_complete` returns the number of complete `Part` messages. And
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//! `SyncKeyGen::is_node_ready` can be used to check whether a particluar node's `Part` is
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//! complete.
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//!
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//! The `Part` and `Ack` messages alone contain all the information needed for anyone to compute
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//! the public key set, and for anyone owning one of the participating secret keys to compute
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//! their own secret key share. In particular:
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//! * Observer nodes can also use `SyncKeyGen`. For observers, no `Part` and `Ack`
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//! messages will be created and they do not need to send anything. On completion, they will only
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//! receive the public key set, but no secret key share.
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//! * If a participant crashed and lost its `SyncKeyGen` instance, but still has its original
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//! key pair, and if the key generation messages were committed to some public ledger, it can
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//! create a new `SyncKeyGen`, handle all the messages in order, and compute its secret key share.
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//!
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//! ## Example
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//!
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//! ```
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//! use std::collections::BTreeMap;
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//! use std::sync::Arc;
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//!
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//! use threshold_crypto::{SecretKey, SignatureShare};
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//! use hbbft::sync_key_gen::{to_pub_keys, AckOutcome, PartOutcome, PubKeyMap, SyncKeyGen};
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//!
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//! // Use the OS random number generator for any randomness:
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//! let mut rng = rand::rngs::OsRng::new().expect("Could not open OS random number generator.");
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//!
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//! // Two out of four shares will suffice to sign or encrypt something.
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//! let (threshold, node_num) = (1, 4);
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//!
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//! // Generate individual key pairs for encryption. These are not suitable for threshold schemes.
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//! let sec_keys: Vec<SecretKey> = (0..node_num).map(|_| rand::random()).collect();
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//! let pub_keys = to_pub_keys(sec_keys.iter().enumerate());
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//!
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//! // Create the `SyncKeyGen` instances. The constructor also outputs the part that needs to
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//! // be sent to all other participants, so we save the parts together with their sender ID.
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//! let mut nodes = BTreeMap::new();
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//! let mut parts = Vec::new();
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//! for (id, sk) in sec_keys.into_iter().enumerate() {
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//! let (sync_key_gen, opt_part) = SyncKeyGen::new(
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//! id,
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//! sk,
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//! pub_keys.clone(),
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//! threshold,
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//! &mut rng,
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//! ).unwrap_or_else(|_| panic!("Failed to create `SyncKeyGen` instance for node #{}", id));
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//! nodes.insert(id, sync_key_gen);
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//! parts.push((id, opt_part.unwrap())); // Would be `None` for observer nodes.
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//! }
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//!
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//! // All nodes now handle the parts and send the resulting `Ack` messages.
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//! let mut acks = Vec::new();
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//! for (sender_id, part) in parts {
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//! for (&id, node) in &mut nodes {
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//! match node
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//! .handle_part(&sender_id, part.clone(), &mut rng)
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//! .expect("Failed to handle Part")
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//! {
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//! PartOutcome::Valid(Some(ack)) => acks.push((id, ack)),
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//! PartOutcome::Invalid(fault) => panic!("Invalid Part: {:?}", fault),
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//! PartOutcome::Valid(None) => {
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//! panic!("We are not an observer, so we should send Ack.")
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//! }
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//! }
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//! }
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//! }
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//!
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//! // Finally, we handle all the `Ack`s.
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//! for (sender_id, ack) in acks {
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//! for node in nodes.values_mut() {
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//! match node.handle_ack(&sender_id, ack.clone()).expect("Failed to handle Ack") {
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//! AckOutcome::Valid => (),
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//! AckOutcome::Invalid(fault) => panic!("Invalid Ack: {:?}", fault),
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//! }
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//! }
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//! }
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//!
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//! // We have all the information and can generate the key sets.
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//! // Generate the public key set; which is identical for all nodes.
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//! let pub_key_set = nodes[&0].generate().expect("Failed to create `PublicKeySet` from node #0").0;
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//! let mut secret_key_shares = BTreeMap::new();
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//! for (&id, node) in &mut nodes {
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//! assert!(node.is_ready());
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//! let (pks, opt_sks) = node.generate().unwrap_or_else(|_|
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//! panic!("Failed to create `PublicKeySet` and `SecretKeyShare` for node #{}", id)
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//! );
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//! assert_eq!(pks, pub_key_set); // All nodes now know the public keys and public key shares.
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//! let sks = opt_sks.expect("Not an observer node: We receive a secret key share.");
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//! secret_key_shares.insert(id, sks);
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//! }
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//!
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//! // Two out of four nodes can now sign a message. Each share can be verified individually.
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//! let msg = "Nodes 0 and 1 does not agree with this.";
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//! let mut sig_shares: BTreeMap<usize, SignatureShare> = BTreeMap::new();
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//! for (&id, sks) in &secret_key_shares {
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//! if id != 0 && id != 1 {
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//! let sig_share = sks.sign(msg);
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//! let pks = pub_key_set.public_key_share(id);
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//! assert!(pks.verify(&sig_share, msg));
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//! sig_shares.insert(id, sig_share);
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//! }
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//! }
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//!
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//! // Two signatures are over the threshold. They are enough to produce a signature that matches
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//! // the public master key.
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//! let sig = pub_key_set
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//! .combine_signatures(&sig_shares)
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//! .expect("The shares can be combined.");
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//! assert!(pub_key_set.public_key().verify(&sig, msg));
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//! ```
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//!
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//! ## How it works
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//!
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//! The algorithm is based on ideas from
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//! [Distributed Key Generation in the Wild](https://eprint.iacr.org/2012/377.pdf) and
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//! [A robust threshold elliptic curve digital signature providing a new verifiable secret sharing scheme](https://www.researchgate.net/profile/Ihab_Ali/publication/4205262_A_robust_threshold_elliptic_curve_digital_signature_providing_a_new_verifiable_secret_sharing_scheme/links/02e7e538f15726323a000000/A-robust-threshold-elliptic-curve-digital-signature-providing-a-new-verifiable-secret-sharing-scheme.pdf?origin=publication_detail).
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//!
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//! In a trusted dealer scenario, the following steps occur:
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//!
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//! 1. Dealer generates a `BivarPoly` of degree _t_ and publishes the `BivarCommitment` which is
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//! used to publicly verify the polynomial's values.
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//! 2. Dealer sends _row_ _m > 0_ to node number _m_.
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//! 3. Node _m_, in turn, sends _value_ number _s_ to node number _s_.
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//! 4. This process continues until _2 t + 1_ nodes confirm they have received a valid row. If
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//! there are at most _t_ faulty nodes, we know that at least _t + 1_ correct nodes sent on an
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//! entry of every other node's column to that node.
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//! 5. This means every node can reconstruct its column, and the value at _0_ of its column.
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//! 6. These values all lie on a univariate polynomial of degree _t_ and can be used as secret keys.
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//!
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//! In our _dealerless_ environment, at least _t + 1_ nodes each generate a polynomial using the
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//! method above. The sum of the secret keys we received from each node is then used as our secret
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//! key. No single node knows the secret master key.
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use std::borrow::Borrow;
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use std::collections::{BTreeMap, BTreeSet};
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use std::fmt::{self, Debug, Formatter};
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use std::string::ToString;
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use std::sync::Arc;
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use bincode;
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use failure::Fail;
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use rand::{self, Rng};
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use serde::{Deserialize, Serialize};
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use crate::crypto::{
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self,
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error::Error as CryptoError,
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poly::{BivarCommitment, BivarPoly, Poly},
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serde_impl::FieldWrap,
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Fr, G1Affine, PublicKeySet, SecretKeyShare,
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};
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use crate::pairing::{CurveAffine, Field};
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use crate::NodeIdT;
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/// A cryptographic key that allows decrypting messages that were encrypted to the key's owner.
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pub trait SecretKey {
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/// The decryption error type.
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type Error: ToString;
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/// Decrypts a ciphertext.
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fn decrypt(&self, ct: &[u8]) -> Result<Vec<u8>, Self::Error>;
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}
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/// A cryptographic public key that allows encrypting messages to the key's owner.
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pub trait PublicKey {
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/// The encryption error type.
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type Error: ToString;
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/// The corresponding secret key type. The secret key is known only to the key's owner.
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type SecretKey: SecretKey;
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/// Encrypts a message to this key's owner and returns the ciphertext.
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fn encrypt<M: AsRef<[u8]>, R: Rng>(&self, msg: M, rng: &mut R) -> Result<Vec<u8>, Self::Error>;
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}
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impl SecretKey for crypto::SecretKey {
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type Error = bincode::Error;
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fn decrypt(&self, ct: &[u8]) -> Result<Vec<u8>, bincode::Error> {
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self.decrypt(&bincode::deserialize(ct)?)
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.ok_or_else(|| bincode::ErrorKind::Custom("Invalid ciphertext.".to_string()).into())
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}
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}
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impl PublicKey for crypto::PublicKey {
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type Error = bincode::Error;
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type SecretKey = crypto::SecretKey;
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fn encrypt<M: AsRef<[u8]>, R: Rng>(
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&self,
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msg: M,
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rng: &mut R,
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) -> Result<Vec<u8>, bincode::Error> {
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bincode::serialize(&self.encrypt_with_rng(rng, msg))
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}
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}
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/// A map assigning to each node ID a public key, wrapped in an `Arc`.
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pub type PubKeyMap<N, PK = crypto::PublicKey> = Arc<BTreeMap<N, PK>>;
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/// Returns a `PubKeyMap` corresponding to the given secret keys.
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///
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/// This is mostly useful for setting up test networks.
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pub fn to_pub_keys<'a, I, B, N: NodeIdT + 'a>(sec_keys: I) -> PubKeyMap<N>
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where
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B: Borrow<N>,
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I: IntoIterator<Item = (B, &'a crypto::SecretKey)>,
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{
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let to_pub = |(id, sk): I::Item| (id.borrow().clone(), sk.public_key());
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Arc::new(sec_keys.into_iter().map(to_pub).collect())
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}
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/// A local error while handling an `Ack` or `Part` message, that was not caused by that message
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/// being invalid.
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#[derive(Clone, Eq, PartialEq, Debug, Fail)]
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pub enum Error {
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/// Error creating `SyncKeyGen`.
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#[fail(display = "Error creating SyncKeyGen: {}", _0)]
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Creation(CryptoError),
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/// Error generating keys.
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#[fail(display = "Error generating keys: {}", _0)]
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Generation(CryptoError),
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/// Unknown sender.
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#[fail(display = "Unknown sender")]
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UnknownSender,
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/// Failed to serialize message.
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#[fail(display = "Serialization error: {}", _0)]
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Serialize(String),
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/// Failed to encrypt message parts for a peer.
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#[fail(display = "Encryption error: {}", _0)]
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Encrypt(String),
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}
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impl From<bincode::Error> for Error {
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fn from(err: bincode::Error) -> Error {
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Error::Serialize(format!("{:?}", err))
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}
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}
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impl Error {
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fn encrypt<E: ToString>(err: E) -> Error {
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Error::Encrypt(err.to_string())
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}
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}
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/// A submission by a validator for the key generation. It must to be sent to all participating
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/// nodes and handled by all of them, including the one that produced it.
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///
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/// The message contains a commitment to a bivariate polynomial, and for each node, an encrypted
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/// row of values. If this message receives enough `Ack`s, it will be used as summand to produce
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/// the the key set in the end.
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#[derive(Deserialize, Serialize, Clone, Hash, Eq, PartialEq)]
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pub struct Part(BivarCommitment, Vec<Vec<u8>>);
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impl Debug for Part {
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fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
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f.debug_tuple("Part")
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.field(&format!("<degree {}>", self.0.degree()))
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.field(&format!("<{} rows>", self.1.len()))
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.finish()
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}
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}
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/// A confirmation that we have received and verified a validator's part. It must be sent to
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/// all participating nodes and handled by all of them, including ourselves.
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///
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/// The message is only produced after we verified our row against the commitment in the `Part`.
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/// For each node, it contains one encrypted value of that row.
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#[derive(Deserialize, Serialize, Clone, Hash, Eq, PartialEq)]
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pub struct Ack(u64, Vec<Vec<u8>>);
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impl Debug for Ack {
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fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
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f.debug_tuple("Ack")
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.field(&self.0)
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.field(&format!("<{} values>", self.1.len()))
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.finish()
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}
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}
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/// The information needed to track a single proposer's secret sharing process.
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#[derive(Debug, PartialEq, Eq)]
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struct ProposalState {
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/// The proposer's commitment.
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commit: BivarCommitment,
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/// The verified values we received from `Ack` messages.
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values: BTreeMap<u64, Fr>,
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/// The nodes which have acked this part, valid or not.
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acks: BTreeSet<u64>,
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}
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impl ProposalState {
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/// Creates a new part state with a commitment.
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fn new(commit: BivarCommitment) -> ProposalState {
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ProposalState {
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commit,
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values: BTreeMap::new(),
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acks: BTreeSet::new(),
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}
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}
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/// Returns `true` if at least `2 * threshold + 1` nodes have acked.
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fn is_complete(&self, threshold: usize) -> bool {
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self.acks.len() > 2 * threshold
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}
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}
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/// The outcome of handling and verifying a `Part` message.
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pub enum PartOutcome {
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/// The message was valid: the part of it that was encrypted to us matched the public
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/// commitment, so we can multicast an `Ack` message for it. If we are an observer or we have
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/// already handled the same `Part` before, this contains `None` instead.
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Valid(Option<Ack>),
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/// The message was invalid: We now know that the proposer is faulty, and dont' send an `Ack`.
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Invalid(PartFault),
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}
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/// The outcome of handling and verifying an `Ack` message.
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pub enum AckOutcome {
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/// The message was valid.
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Valid,
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/// The message was invalid: The sender is faulty.
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Invalid(AckFault),
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}
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/// A synchronous algorithm for dealerless distributed key generation.
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///
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/// It requires that all nodes handle all messages in the exact same order.
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#[derive(Debug)]
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pub struct SyncKeyGen<N, PK: PublicKey = crypto::PublicKey> {
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/// Our node ID.
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our_id: N,
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/// Our node index.
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our_idx: Option<u64>,
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/// Our secret key.
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sec_key: PK::SecretKey,
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/// The public keys of all nodes, by node ID.
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pub_keys: PubKeyMap<N, PK>,
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/// Proposed bivariate polynomials.
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parts: BTreeMap<u64, ProposalState>,
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/// The degree of the generated polynomial.
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threshold: usize,
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}
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impl<N: NodeIdT, PK: PublicKey> SyncKeyGen<N, PK> {
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/// Creates a new `SyncKeyGen` instance, together with the `Part` message that should be
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/// multicast to all nodes.
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///
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/// If we are not a validator but only an observer, no `Part` message is produced and no
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/// messages need to be sent.
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pub fn new<R: rand::Rng>(
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our_id: N,
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sec_key: PK::SecretKey,
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pub_keys: PubKeyMap<N, PK>,
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threshold: usize,
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rng: &mut R,
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) -> Result<(Self, Option<Part>), Error> {
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let our_idx = pub_keys
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.keys()
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.position(|id| *id == our_id)
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.map(|idx| idx as u64);
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let key_gen = SyncKeyGen {
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our_id,
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our_idx,
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sec_key,
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pub_keys,
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parts: BTreeMap::new(),
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threshold,
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};
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if our_idx.is_none() {
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return Ok((key_gen, None)); // No part: we are an observer.
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}
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let our_part = BivarPoly::random(threshold, rng);
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let commit = our_part.commitment();
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let encrypt = |(i, pk): (usize, &PK)| {
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let row = bincode::serialize(&our_part.row(i + 1))?;
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Ok(pk.encrypt(&row, rng).map_err(Error::encrypt)?)
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};
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let rows = key_gen
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.pub_keys
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.values()
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.enumerate()
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.map(encrypt)
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.collect::<Result<Vec<Vec<u8>>, Error>>()?;
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Ok((key_gen, Some(Part(commit, rows))))
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}
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/// Returns the id of this node.
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pub fn our_id(&self) -> &N {
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&self.our_id
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}
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/// Returns the map of participating nodes and their public keys.
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pub fn public_keys(&self) -> &PubKeyMap<N, PK> {
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&self.pub_keys
|
|
}
|
|
|
|
/// Handles a `Part` message. If it is valid, returns an `Ack` message to be broadcast.
|
|
///
|
|
/// If we are only an observer, `None` is returned instead and no messages need to be sent.
|
|
///
|
|
/// All participating nodes must handle the exact same sequence of messages.
|
|
/// Note that `handle_part` also needs to explicitly be called with this instance's own `Part`.
|
|
pub fn handle_part<R: rand::Rng>(
|
|
&mut self,
|
|
sender_id: &N,
|
|
part: Part,
|
|
rng: &mut R,
|
|
) -> Result<PartOutcome, Error> {
|
|
let sender_idx = self.node_index(sender_id).ok_or(Error::UnknownSender)?;
|
|
let row = match self.handle_part_or_fault(sender_idx, part) {
|
|
Ok(Some(row)) => row,
|
|
Ok(None) => return Ok(PartOutcome::Valid(None)),
|
|
Err(fault) => return Ok(PartOutcome::Invalid(fault)),
|
|
};
|
|
// The row is valid. Encrypt one value for each node and broadcast an `Ack`.
|
|
let mut values = Vec::new();
|
|
for (idx, pk) in self.pub_keys.values().enumerate() {
|
|
let val = row.evaluate(idx + 1);
|
|
let ser_val = bincode::serialize(&FieldWrap(val))?;
|
|
values.push(pk.encrypt(ser_val, rng).map_err(Error::encrypt)?);
|
|
}
|
|
Ok(PartOutcome::Valid(Some(Ack(sender_idx, values))))
|
|
}
|
|
|
|
/// Handles an `Ack` message.
|
|
///
|
|
/// All participating nodes must handle the exact same sequence of messages.
|
|
/// Note that `handle_ack` also needs to explicitly be called with this instance's own `Ack`s.
|
|
pub fn handle_ack(&mut self, sender_id: &N, ack: Ack) -> Result<AckOutcome, Error> {
|
|
let sender_idx = self.node_index(sender_id).ok_or(Error::UnknownSender)?;
|
|
Ok(match self.handle_ack_or_fault(sender_idx, ack) {
|
|
Ok(()) => AckOutcome::Valid,
|
|
Err(fault) => AckOutcome::Invalid(fault),
|
|
})
|
|
}
|
|
|
|
/// Returns the index of the node, or `None` if it is unknown.
|
|
fn node_index(&self, node_id: &N) -> Option<u64> {
|
|
self.pub_keys
|
|
.keys()
|
|
.position(|id| id == node_id)
|
|
.map(|idx| idx as u64)
|
|
}
|
|
|
|
/// Returns the number of complete parts. If this is at least `threshold + 1`, the keys can
|
|
/// be generated, but it is possible to wait for more to increase security.
|
|
pub fn count_complete(&self) -> usize {
|
|
self.parts
|
|
.values()
|
|
.filter(|part| part.is_complete(self.threshold))
|
|
.count()
|
|
}
|
|
|
|
/// Returns `true` if the part of the given node is complete.
|
|
pub fn is_node_ready(&self, proposer_id: &N) -> bool {
|
|
self.node_index(proposer_id)
|
|
.and_then(|proposer_idx| self.parts.get(&proposer_idx))
|
|
.map_or(false, |part| part.is_complete(self.threshold))
|
|
}
|
|
|
|
/// Returns `true` if enough parts are complete to safely generate the new key.
|
|
pub fn is_ready(&self) -> bool {
|
|
self.count_complete() > self.threshold
|
|
}
|
|
|
|
/// Returns the new secret key share and the public key set.
|
|
///
|
|
/// These are only secure if `is_ready` returned `true`. Otherwise it is not guaranteed that
|
|
/// none of the nodes knows the secret master key.
|
|
///
|
|
/// If we are only an observer node, no secret key share is returned.
|
|
///
|
|
/// All participating nodes must have handled the exact same sequence of `Part` and `Ack`
|
|
/// messages before calling this method. Otherwise their key shares will not match.
|
|
pub fn generate(&self) -> Result<(PublicKeySet, Option<SecretKeyShare>), Error> {
|
|
let mut pk_commit = Poly::zero().commitment();
|
|
let mut opt_sk_val = self.our_idx.map(|_| Fr::zero());
|
|
let is_complete = |part: &&ProposalState| part.is_complete(self.threshold);
|
|
for part in self.parts.values().filter(is_complete) {
|
|
pk_commit += part.commit.row(0);
|
|
if let Some(sk_val) = opt_sk_val.as_mut() {
|
|
let row = Poly::interpolate(part.values.iter().take(self.threshold + 1));
|
|
sk_val.add_assign(&row.evaluate(0));
|
|
}
|
|
}
|
|
let opt_sk = if let Some(mut fr) = opt_sk_val {
|
|
let sk = SecretKeyShare::from_mut(&mut fr);
|
|
Some(sk)
|
|
} else {
|
|
None
|
|
};
|
|
Ok((pk_commit.into(), opt_sk))
|
|
}
|
|
|
|
/// Returns the number of nodes participating in the key generation.
|
|
pub fn num_nodes(&self) -> usize {
|
|
self.pub_keys.len()
|
|
}
|
|
|
|
/// Handles a `Part` message, or returns a `PartFault` if it is invalid.
|
|
fn handle_part_or_fault(
|
|
&mut self,
|
|
sender_idx: u64,
|
|
Part(commit, rows): Part,
|
|
) -> Result<Option<Poly>, PartFault> {
|
|
if rows.len() != self.pub_keys.len() {
|
|
return Err(PartFault::RowCount);
|
|
}
|
|
if let Some(state) = self.parts.get(&sender_idx) {
|
|
if state.commit != commit {
|
|
return Err(PartFault::MultipleParts);
|
|
}
|
|
return Ok(None); // We already handled this `Part` before.
|
|
}
|
|
// Retrieve our own row's commitment, and store the full commitment.
|
|
let opt_idx_commit_row = self.our_idx.map(|idx| (idx, commit.row(idx + 1)));
|
|
self.parts.insert(sender_idx, ProposalState::new(commit));
|
|
let (our_idx, commit_row) = match opt_idx_commit_row {
|
|
Some((idx, row)) => (idx, row),
|
|
None => return Ok(None), // We are only an observer. Nothing to send or decrypt.
|
|
};
|
|
// We are a validator: Decrypt and deserialize our row and compare it to the commitment.
|
|
let ser_row = self
|
|
.sec_key
|
|
.decrypt(&rows[our_idx as usize])
|
|
.map_err(|_| PartFault::DecryptRow)?;
|
|
let row: Poly = bincode::deserialize(&ser_row).map_err(|_| PartFault::DeserializeRow)?;
|
|
if row.commitment() != commit_row {
|
|
return Err(PartFault::RowCommitment);
|
|
}
|
|
Ok(Some(row))
|
|
}
|
|
|
|
/// Handles an `Ack` message, or returns an `AckFault` if it is invalid.
|
|
fn handle_ack_or_fault(
|
|
&mut self,
|
|
sender_idx: u64,
|
|
Ack(proposer_idx, values): Ack,
|
|
) -> Result<(), AckFault> {
|
|
if values.len() != self.pub_keys.len() {
|
|
return Err(AckFault::ValueCount);
|
|
}
|
|
let part = self
|
|
.parts
|
|
.get_mut(&proposer_idx)
|
|
.ok_or(AckFault::MissingPart)?;
|
|
if !part.acks.insert(sender_idx) {
|
|
return Ok(()); // We already handled this `Ack` before.
|
|
}
|
|
let our_idx = match self.our_idx {
|
|
Some(our_idx) => our_idx,
|
|
None => return Ok(()), // We are only an observer. Nothing to decrypt for us.
|
|
};
|
|
// We are a validator: Decrypt and deserialize our value and compare it to the commitment.
|
|
let ser_val = self
|
|
.sec_key
|
|
.decrypt(&values[our_idx as usize])
|
|
.map_err(|_| AckFault::DecryptValue)?;
|
|
let val = bincode::deserialize::<FieldWrap<Fr>>(&ser_val)
|
|
.map_err(|_| AckFault::DeserializeValue)?
|
|
.into_inner();
|
|
if part.commit.evaluate(our_idx + 1, sender_idx + 1) != G1Affine::one().mul(val) {
|
|
return Err(AckFault::ValueCommitment);
|
|
}
|
|
part.values.insert(sender_idx + 1, val);
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
/// An error in an `Ack` message sent by a faulty node.
|
|
#[derive(Clone, Copy, Eq, PartialEq, Debug, Fail)]
|
|
pub enum AckFault {
|
|
/// The number of values differs from the number of nodes.
|
|
#[fail(display = "The number of values differs from the number of nodes")]
|
|
ValueCount,
|
|
/// No corresponding Part received.
|
|
#[fail(display = "No corresponding Part received")]
|
|
MissingPart,
|
|
/// Value decryption failed.
|
|
#[fail(display = "Value decryption failed")]
|
|
DecryptValue,
|
|
/// Value deserialization failed.
|
|
#[fail(display = "Value deserialization failed")]
|
|
DeserializeValue,
|
|
/// Value doesn't match the commitment.
|
|
#[fail(display = "Value doesn't match the commitment")]
|
|
ValueCommitment,
|
|
}
|
|
|
|
/// An error in a `Part` message sent by a faulty node.
|
|
#[derive(Clone, Copy, Eq, PartialEq, Debug, Fail)]
|
|
pub enum PartFault {
|
|
/// The number of rows differs from the number of nodes.
|
|
#[fail(display = "The number of rows differs from the number of nodes")]
|
|
RowCount,
|
|
/// Received multiple different Part messages from the same sender.
|
|
#[fail(display = "Received multiple different Part messages from the same sender")]
|
|
MultipleParts,
|
|
/// Could not decrypt our row in the Part message.
|
|
#[fail(display = "Could not decrypt our row in the Part message")]
|
|
DecryptRow,
|
|
/// Could not deserialize our row in the Part message.
|
|
#[fail(display = "Could not deserialize our row in the Part message")]
|
|
DeserializeRow,
|
|
/// Row does not match the commitment.
|
|
#[fail(display = "Row does not match the commitment")]
|
|
RowCommitment,
|
|
}
|