[Consensus] add Committee type (MystenLabs#15455)

## Description 

Add `Committee` config and crypto key types to the
`consensus-config` crate.

## Test Plan 

CI

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

consensus/config/Cargo.toml

@@ -7,6 +7,9 @@ edition = "2021"
 publish = false
 
 [dependencies]
+fastcrypto.workspace = true
+multiaddr.workspace = true
+rand.workspace = true
 serde.workspace = true
 
 workspace-hack.workspace = true

consensus/config/src/committee.rs

@@ -0,0 +1,173 @@
+// Copyright (c) Mysten Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+use std::fmt::{Display, Formatter};
+
+use multiaddr::Multiaddr;
+use serde::{Deserialize, Serialize};
+
+use crate::{NetworkPublicKey, ProtocolPublicKey};
+
+/// Committee of the consensus protocol is updated each epoch.
+pub type Epoch = u64;
+
+/// Voting power of an authority, roughly proportional to the actual amount of Sui staked
+/// by the authority.
+/// Total stake / voting power of all authorities should sum to 10,000.
+pub type Stake = u64;
+
+/// Committee is the set of authorities that participate in the consensus protocol for this epoch.
+/// Its configuration is stored and computed on chain.
+#[derive(Serialize, Deserialize)]
+pub struct Committee {
+    /// The epoch number of this committee
+    epoch: Epoch,
+    /// Total stake in the committee.
+    total_stake: Stake,
+    /// The quorum threshold (2f+1).
+    quorum_threshold: Stake,
+    /// The validity threshold (f+1).
+    validity_threshold: Stake,
+    /// Protocol and network info of each authority.
+    authorities: Vec<Authority>,
+}
+
+impl Committee {
+    pub fn new(epoch: Epoch, authorities: Vec<Authority>) -> Self {
+        assert!(!authorities.is_empty(), "Committee cannot be empty!");
+        assert!(
+            authorities.len() < u32::MAX as usize,
+            "Too many authorities ({})!",
+            authorities.len()
+        );
+        let total_stake = authorities.iter().map(|a| a.stake).sum();
+        assert_ne!(total_stake, 0, "Total stake cannot be zero!");
+        let quorum_threshold = 2 * total_stake / 3 + 1;
+        let validity_threshold = (total_stake + 2) / 3;
+        Self {
+            epoch,
+            total_stake,
+            quorum_threshold,
+            validity_threshold,
+            authorities,
+        }
+    }
+
+    /// Public accessors for Committee data.
+
+    pub fn epoch(&self) -> Epoch {
+        self.epoch
+    }
+
+    pub fn total_stake(&self) -> Stake {
+        self.total_stake
+    }
+
+    pub fn quorum_threshold(&self) -> Stake {
+        self.quorum_threshold
+    }
+
+    pub fn validity_threshold(&self) -> Stake {
+        self.validity_threshold
+    }
+
+    pub fn stake(&self, authority_index: AuthorityIndex) -> Stake {
+        self.authorities[authority_index.value()].stake
+    }
+
+    pub fn authority(&self, authority_index: AuthorityIndex) -> &Authority {
+        &self.authorities[authority_index.value()]
+    }
+
+    pub fn authorities(&self) -> impl Iterator<Item = (AuthorityIndex, &Authority)> {
+        self.authorities
+            .iter()
+            .enumerate()
+            .map(|(i, a)| (AuthorityIndex(i as u32), a))
+    }
+
+    pub fn size(&self) -> usize {
+        self.authorities.len()
+    }
+}
+
+/// Represents one authority in the committee.
+///
+/// NOTE: this is intentionally un-cloneable, to encourage only copying relevant fields.
+/// AuthorityIndex should be used to reference an authority instead.
+#[derive(Serialize, Deserialize)]
+pub struct Authority {
+    /// Voting power of the authority in the committee.
+    pub stake: Stake,
+    /// Network address for communicating with the authority.
+    pub address: Multiaddr,
+    /// The validator's hostname, for metrics and logging.
+    pub hostname: String,
+    /// The authority's ed25519 publicKey for signing network messages and blocks.
+    pub network_key: NetworkPublicKey,
+    /// The authority's bls public key for random beacon.
+    pub protocol_key: ProtocolPublicKey,
+}
+
+/// Each authority is uniquely identified by its AuthorityIndex in the Committee.
+/// AuthorityIndex is between 0 (inclusive) and the total number of authorities (exclusive).
+///
+/// NOTE: AuthorityIndex should not need to be created outside of this file or incremented.
+#[derive(
+    Eq, PartialEq, Ord, PartialOrd, Clone, Copy, Debug, Default, Hash, Serialize, Deserialize,
+)]
+pub struct AuthorityIndex(u32);
+
+impl AuthorityIndex {
+    pub fn value(&self) -> usize {
+        self.0 as usize
+    }
+}
+
+impl Display for AuthorityIndex {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.0.to_string().as_str())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{Authority, Committee, NetworkKeyPair, ProtocolKeyPair, Stake};
+    use fastcrypto::traits::KeyPair as _;
+    use multiaddr::Multiaddr;
+    use rand::{rngs::StdRng, SeedableRng};
+
+    #[test]
+    fn committee_basic() {
+        // GIVEN
+        let epoch = 100;
+
+        let mut authorities = vec![];
+        let mut rng = StdRng::from_seed([9; 32]);
+        let num_of_authorities = 9;
+        for i in 1..=num_of_authorities {
+            let network_keypair = NetworkKeyPair::generate(&mut rng);
+            let protocol_keypair = ProtocolKeyPair::generate(&mut rng);
+            authorities.push(Authority {
+                stake: i as Stake,
+                address: Multiaddr::empty(),
+                hostname: "test_host".to_string(),
+                network_key: network_keypair.public().clone(),
+                protocol_key: protocol_keypair.public().clone(),
+            });
+        }
+
+        let committee = Committee::new(epoch, authorities);
+
+        // THEN make sure the output Committee fields are populated correctly.
+        assert_eq!(committee.size(), num_of_authorities);
+        for (i, authority) in committee.authorities() {
+            assert_eq!((i.value() + 1) as Stake, authority.stake);
+        }
+
+        // AND ensure thresholds are calculated correctly.
+        assert_eq!(committee.total_stake(), 45);
+        assert_eq!(committee.quorum_threshold(), 31);
+        assert_eq!(committee.validity_threshold(), 15);
+    }
+}

consensus/config/src/crypto.rs

@@ -0,0 +1,28 @@
+// Copyright (c) Mysten Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+use fastcrypto::{bls12381, ed25519};
+
+////////////////////////////////////////////////////////////////////////
+// Type aliases selecting the cryptography algorithms for the code base.
+////////////////////////////////////////////////////////////////////////
+// Here we select the types that are used by default in the code base.
+// The whole code base should only:
+// - refer to those aliases and not use the individual scheme implementations
+// - not use the schemes in a way that break genericity (e.g. using their Struct impl functions)
+// - swap one of those aliases to point to another type if necessary
+//
+// Beware: if you change those aliases to point to another scheme implementation, you will have
+// to change all four aliases to point to concrete types that work with each other. Failure to do
+// so will result in a ton of compilation errors, and worse: it will not make sense!
+
+/// Network key signs network messages and blocks.
+pub type NetworkPublicKey = ed25519::Ed25519PublicKey;
+pub type NetworkPrivateKey = ed25519::Ed25519PrivateKey;
+pub type NetworkKeyPair = ed25519::Ed25519KeyPair;
+
+/// Protocol key is used in random beacon.
+pub type ProtocolPublicKey = bls12381::min_sig::BLS12381PublicKey;
+pub type ProtocolPublicKeyBytes = bls12381::min_sig::BLS12381PublicKeyAsBytes;
+pub type ProtocolPrivateKey = bls12381::min_sig::BLS12381PrivateKey;
+pub type ProtocolKeyPair = bls12381::min_sig::BLS12381KeyPair;

consensus/config/src/lib.rs

@@ -1,6 +1,10 @@
 // Copyright (c) Mysten Labs, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-pub mod parameters;
+mod committee;
+mod crypto;
+mod parameters;
 
-pub use parameters::Parameters;
+pub use committee::*;
+pub use crypto::*;
+pub use parameters::*;

consensus/config/tests/committee_test.rs

@@ -0,0 +1,34 @@
+// Copyright (c) Mysten Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+use consensus_config::{Authority, Committee, NetworkKeyPair, ProtocolKeyPair, Stake};
+use fastcrypto::traits::KeyPair as _;
+use insta::assert_yaml_snapshot;
+use multiaddr::Multiaddr;
+use rand::{rngs::StdRng, SeedableRng as _};
+
+// Committee is not sent over network or stored on disk itself, but some of its fields are.
+// So this test can still be useful to detect accidental format changes.
+#[test]
+fn committee_snapshot_matches() {
+    let epoch = 100;
+
+    let mut authorities: Vec<_> = vec![];
+    let mut rng = StdRng::from_seed([9; 32]);
+    let num_of_authorities = 10;
+    for i in 1..=num_of_authorities {
+        let network_keypair = NetworkKeyPair::generate(&mut rng);
+        let protocol_keypair = ProtocolKeyPair::generate(&mut rng);
+        authorities.push(Authority {
+            stake: i as Stake,
+            address: Multiaddr::empty(),
+            hostname: "test_host".to_string(),
+            network_key: network_keypair.public().clone(),
+            protocol_key: protocol_keypair.public().clone(),
+        });
+    }
+
+    let committee = Committee::new(epoch, authorities);
+
+    assert_yaml_snapshot!("committee", committee)
+}

consensus/config/tests/snapshots/committee_test__committee.snap

@@ -0,0 +1,60 @@
+---
+source: consensus/config/tests/committee_test.rs
+expression: committee
+---
+epoch: 100
+total_stake: 55
+quorum_threshold: 37
+validity_threshold: 19
+authorities:
+  - stake: 1
+    address: ""
+    hostname: test_host
+    network_key: lscBzpFcgepvETNDWHp61B+teyauHrk6kb5XBszDufg=
+    protocol_key: tembhBjGw+XVGXywAYDja1R67d8pSKGhYypbgeRUJmTTdzfNnr/LHJ3U0bZY49ChGXw6mKwBVJV4KP3na8YFaef9wQuHKgwjvhJT3FnimCPyBwIz4cFasq1d3As4/yeP
+  - stake: 2
+    address: ""
+    hostname: test_host
+    network_key: VnXFtZxaTby9AquydHFr9dy8+GlVoPcsm8icljGTbWQ=
+    protocol_key: hLIJiig6cqajwuIlnxjL+bxhZxCgEWUGdN9VyJSqMAvuN6tDm7qTcBplvDICmgSlGJwHZ5IzyOH6N+Wj1Fa1odxsM86eLf9g+MjzT/h869sqV9EpyXtpYbufPYCW0fkT
+  - stake: 3
+    address: ""
+    hostname: test_host
+    network_key: +yTI/ZSBZa9CmHP/Qhjtf2bgTR0lC+9NUP8BgQq0OPw=
+    protocol_key: kci5lWPW4LlAr1jLSyEkGtYeSfstp3daJ0pChi5zo4KaDOOQd7IbnRPyP/zMqkfTE9MIyymjSkhnI72/Wogbqedrc5lhIp+C2wtbv79mdC8SrbHb2Y/LHvYD7w1mOJFM
+  - stake: 4
+    address: ""
+    hostname: test_host
+    network_key: TLb93AG1NlYtf9dVMnS6LJE5aRfqt2LsSBJeuoa3wHk=
+    protocol_key: onGDFBk46p2hpQFq3QJbyAVD0G05FOxRaJQH3LacRTRRfdXWLtewyUi1Z0MMX4H3CpoldjqoGeMbESvqgTZeKt6HE3d8pn6TApMzf632WI3DfUGUUMBM7ciCivNaKTBS
+  - stake: 5
+    address: ""
+    hostname: test_host
+    network_key: 7DYZ4De7EKRhhH0GBMTKlBqUeXnFMgkzLKjekMAuesw=
+    protocol_key: iM3E2wCApVtOKv1I/jSpNXO1kPRCnHo0c6H/qgyxvJngmgW1KYnWtycts8drNLIUGLtinT83V8D3Xnc3whUAqiKYrJ5vu2knQXqFBCmgrqo7N0xZ0T/uuKVWjoNqyHHl
+  - stake: 6
+    address: ""
+    hostname: test_host
+    network_key: B2I7VErvTa/POXtLemf+iDEt/966mNqq3F+DdHcvi8U=
+    protocol_key: pEiGWt/9mL2YXfHkYntXWy7OzGdS1psbJQ2D5Xp5FS7XZWYQzh7+zz/bkOfgWCRaFoV8bbsmb7eVwuMvOTnPvCSamtyUQ3pc+SKVTsXtRbwRNvWtXjTVHGQQSXE5R1kp
+  - stake: 7
+    address: ""
+    hostname: test_host
+    network_key: wCXBPdpdazlmPWntDXu+LQJiJZb72na9EY3njPLgBGY=
+    protocol_key: irfuZhbsh3mvm53TmiAPGWzDUEmr89RhBBtwNGwZOW36BOaSpxcgOZXfrOPTJDstDFU+o1XRq2T0t39P4tKagKjC50TFtMSVFU/4Qf6bHqEPzuZiOtCa3W3mKQUXz8wE
+  - stake: 8
+    address: ""
+    hostname: test_host
+    network_key: +0ebVcUY7X8QIafWGbUmzlhy/Vc2LtNRqqLzk4NgLoU=
+    protocol_key: jDvXpT0oTY7w9BWERszWiLBu9Aajj9WbbPkfmE9M+ijxGCooLK14P1lsqOZ67XMoAIfh8Z5t/hNanV5fH+3PtJT6o8APO5pCoTcLi5SoScRSQKMCevHqHAizI57wG4cl
+  - stake: 9
+    address: ""
+    hostname: test_host
+    network_key: YxoEz+3fDnLfrOkpqVkRxfj/HqlqsoQqt9bzSLjxJEc=
+    protocol_key: iIEIwu3rHEXU1fy+2VNUKjqV2tFLcu35a5Uo+qO99rQ63nywUvOsiDxrUvzOpJYoDZ/Xa4PnzgkhFTiGVi/Qt6ASIBhu/66jjxhDs6Pt7h1CtRFnD3zWRkgYinIzmxuQ
+  - stake: 10
+    address: ""
+    hostname: test_host
+    network_key: lT6jnl+ZiC2MhDfooUetAJFDd6cRQy1Lq9KKjKqOevo=
+    protocol_key: lxvqS7Rm/l8gmFj6Q3CJ3Qv994gzsM/hSt5YoBrE8v4UmfoyuvQ0JQ9gw2qNbMuiDwvkCAxotLiCa0yjKjZe5Kk8QS37dGZw5akNHQ2SHkc+CK7bccWVkdfRnF4iQal5
+