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Merge pull request #70 from poanetwork/afck-sync-key-gen 

Implement SyncKeyGen.
This commit is contained in:
Vladimir Komendantskiy 2018-06-22 10:10:15 +01:00 committed by GitHub
parent 58c1a7e15d 67dbada49f
commit b6f5bf1ce7
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
13 changed files with 662 additions and 273 deletions
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2
README.md
View File

@ -33,6 +33,8 @@ In an optimal networking environment, output includes data sent from each node.
- [x] **[Coin](https://github.com/poanetwork/hbbft/blob/master/src/common_coin.rs):** A pseudorandom binary value used by the Binary Agreement protocol.
- [x] **[Synchronous Key Generation](https://github.com/poanetwork/hbbft/blob/master/src/sync_key_gen.rs)** A dealerless algorithm that generates keys for threshold encryption and signing. Unlike the other algorithms, this one is _completely synchronous_ and should run on top of Honey Badger (or another consensus algorithm)
## Getting Started
This library requires a distributed network environment to function. Details on network requirements TBD.

3
examples/simulation.rs
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@ -19,7 +19,6 @@ use std::{cmp, u64};
use colored::*;
use docopt::Docopt;
use itertools::Itertools;
use pairing::bls12_381::Bls12;
use rand::Rng;
use serde::de::DeserializeOwned;
use serde::Serialize;
@ -428,7 +427,7 @@ fn main() {
println!();
let num_good_nodes = args.flag_n - args.flag_f;
let txs = (0..args.flag_txs).map(|_| Transaction::new(args.flag_tx_size));
let sk_set = SecretKeySet::<Bls12>::random(args.flag_f, &mut rand::thread_rng());
let sk_set = SecretKeySet::random(args.flag_f, &mut rand::thread_rng());
let pk_set = sk_set.public_keys();
let new_honey_badger = |id: NodeUid, all_ids: BTreeSet<NodeUid>| {
let netinfo = Rc::new(NetworkInfo::new(

19
src/common_coin.rs
View File

@ -4,8 +4,6 @@ use std::collections::{BTreeMap, VecDeque};
use std::fmt::Debug;
use std::rc::Rc;
use pairing::bls12_381::Bls12;
use crypto::error as cerror;
use crypto::Signature;
use messaging::{DistAlgorithm, NetworkInfo, Target, TargetedMessage};
@ -26,14 +24,14 @@ error_chain! {
}
#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
pub struct CommonCoinMessage(Signature<Bls12>);
pub struct CommonCoinMessage(Signature);
impl CommonCoinMessage {
pub fn new(sig: Signature<Bls12>) -> Self {
pub fn new(sig: Signature) -> Self {
CommonCoinMessage(sig)
}
pub fn to_sig(&self) -> &Signature<Bls12> {
pub fn to_sig(&self) -> &Signature {
&self.0
}
}
@ -51,7 +49,7 @@ pub struct CommonCoin<NodeUid, T> {
/// Outgoing message queue.
messages: VecDeque<CommonCoinMessage>,
/// All received threshold signature shares.
received_shares: BTreeMap<NodeUid, Signature<Bls12>>,
received_shares: BTreeMap<NodeUid, Signature>,
/// Whether we provided input to the common coin.
had_input: bool,
/// Termination flag.
@ -134,7 +132,7 @@ where
self.handle_share(&id, share)
}
fn handle_share(&mut self, sender_id: &NodeUid, share: Signature<Bls12>) -> Result<()> {
fn handle_share(&mut self, sender_id: &NodeUid, share: Signature) -> Result<()> {
if let Some(i) = self.netinfo.node_index(sender_id) {
let pk_i = self.netinfo.public_key_set().public_key_share(*i as u64);
if !pk_i.verify(&share, &self.nonce) {
@ -156,16 +154,15 @@ where
}
}
fn combine_and_verify_sig(&self) -> Result<Signature<Bls12>> {
fn combine_and_verify_sig(&self) -> Result<Signature> {
// Pass the indices of sender nodes to `combine_signatures`.
let ids_shares: BTreeMap<&NodeUid, &Signature<Bls12>> =
self.received_shares.iter().collect();
let ids_shares: BTreeMap<&NodeUid, &Signature> = self.received_shares.iter().collect();
let ids_u64: BTreeMap<&NodeUid, u64> = ids_shares
.keys()
.map(|&id| (id, *self.netinfo.node_index(id).unwrap() as u64))
.collect();
// Convert indices to `u64` which is an interface type for `pairing`.
let shares: BTreeMap<&u64, &Signature<Bls12>> = ids_shares
let shares: BTreeMap<&u64, &Signature> = ids_shares
.iter()
.map(|(id, &share)| (&ids_u64[id], share))
.collect();

241
src/crypto/mod.rs
View File

@ -1,8 +1,12 @@
// Clippy warns that it's dangerous to derive `PartialEq` and explicitly implement `Hash`, but the
// `pairing::bls12_381` types don't implement `Hash`, so we can't derive it.
#![cfg_attr(feature = "cargo-clippy", allow(derive_hash_xor_eq))]
pub mod error;
pub mod poly;
#[cfg(feature = "serialization-protobuf")]
pub mod protobuf_impl;
mod serde_impl;
pub mod serde_impl;
use std::fmt;
use std::hash::{Hash, Hasher};
@ -10,6 +14,7 @@ use std::hash::{Hash, Hasher};
use byteorder::{BigEndian, ByteOrder};
use clear_on_drop::ClearOnDrop;
use init_with::InitWith;
use pairing::bls12_381::{Bls12, Fr, FrRepr, G1, G1Affine, G2, G2Affine};
use pairing::{CurveAffine, CurveProjective, Engine, Field, PrimeField};
use rand::{ChaChaRng, OsRng, Rng, SeedableRng};
use ring::digest;
@ -24,48 +29,42 @@ const CHACHA_RNG_SEED_SIZE: usize = 8;
const ERR_OS_RNG: &str = "could not initialize the OS random number generator";
/// A public key, or a public key share.
#[derive(Deserialize, Serialize, Clone, Debug)]
pub struct PublicKey<E: Engine>(#[serde(with = "serde_impl::projective")] E::G1);
#[derive(Deserialize, Serialize, Clone, Debug, PartialEq, Eq)]
pub struct PublicKey(#[serde(with = "serde_impl::projective")] G1);
impl<E: Engine> PartialEq for PublicKey<E> {
fn eq(&self, other: &PublicKey<E>) -> bool {
self.0 == other.0
}
}
impl<E: Engine> Hash for PublicKey<E> {
impl Hash for PublicKey {
fn hash<H: Hasher>(&self, state: &mut H) {
self.0.into_affine().into_compressed().as_ref().hash(state);
}
}
impl<E: Engine> PublicKey<E> {
/// Returns `true` if the signature matches the element of `E::G2`.
pub fn verify_g2<H: Into<E::G2Affine>>(&self, sig: &Signature<E>, hash: H) -> bool {
E::pairing(self.0, hash) == E::pairing(E::G1Affine::one(), sig.0)
impl PublicKey {
/// Returns `true` if the signature matches the element of `G2`.
pub fn verify_g2<H: Into<G2Affine>>(&self, sig: &Signature, hash: H) -> bool {
Bls12::pairing(self.0, hash) == Bls12::pairing(G1Affine::one(), sig.0)
}
/// Returns `true` if the signature matches the message.
pub fn verify<M: AsRef<[u8]>>(&self, sig: &Signature<E>, msg: M) -> bool {
self.verify_g2(sig, hash_g2::<E, M>(msg))
pub fn verify<M: AsRef<[u8]>>(&self, sig: &Signature, msg: M) -> bool {
self.verify_g2(sig, hash_g2(msg))
}
/// Returns `true` if the decryption share matches the ciphertext.
pub fn verify_decryption_share(&self, share: &DecryptionShare<E>, ct: &Ciphertext<E>) -> bool {
pub fn verify_decryption_share(&self, share: &DecryptionShare, ct: &Ciphertext) -> bool {
let Ciphertext(ref u, ref v, ref w) = *ct;
let hash = hash_g1_g2::<E, _>(*u, v);
E::pairing(share.0, hash) == E::pairing(self.0, *w)
let hash = hash_g1_g2(*u, v);
Bls12::pairing(share.0, hash) == Bls12::pairing(self.0, *w)
}
/// Encrypts the message.
pub fn encrypt<M: AsRef<[u8]>>(&self, msg: M) -> Ciphertext<E> {
let r: E::Fr = OsRng::new().expect(ERR_OS_RNG).gen();
let u = E::G1Affine::one().mul(r);
pub fn encrypt<M: AsRef<[u8]>>(&self, msg: M) -> Ciphertext {
let r: Fr = OsRng::new().expect(ERR_OS_RNG).gen();
let u = G1Affine::one().mul(r);
let v: Vec<u8> = {
let g = self.0.into_affine().mul(r);
xor_vec(&hash_bytes::<E>(g, msg.as_ref().len()), msg.as_ref())
xor_vec(&hash_bytes(g, msg.as_ref().len()), msg.as_ref())
};
let w = hash_g1_g2::<E, _>(u, &v).into_affine().mul(r);
let w = hash_g1_g2(u, &v).into_affine().mul(r);
Ciphertext(u, v, w)
}
@ -76,10 +75,10 @@ impl<E: Engine> PublicKey<E> {
}
/// A signature, or a signature share.
#[derive(Deserialize, Serialize, Clone)]
pub struct Signature<E: Engine>(#[serde(with = "serde_impl::projective")] E::G2);
#[derive(Deserialize, Serialize, Clone, PartialEq, Eq)]
pub struct Signature(#[serde(with = "serde_impl::projective")] G2);
impl<E: Engine> fmt::Debug for Signature<E> {
impl fmt::Debug for Signature {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let uncomp = self.0.into_affine().into_uncompressed();
let bytes = uncomp.as_ref();
@ -87,19 +86,13 @@ impl<E: Engine> fmt::Debug for Signature<E> {
}
}
impl<E: Engine> PartialEq for Signature<E> {
fn eq(&self, other: &Signature<E>) -> bool {
self.0 == other.0
}
}
impl<E: Engine> Hash for Signature<E> {
impl Hash for Signature {
fn hash<H: Hasher>(&self, state: &mut H) {
self.0.into_affine().into_compressed().as_ref().hash(state);
}
}
impl<E: Engine> Signature<E> {
impl Signature {
pub fn parity(&self) -> bool {
let uncomp = self.0.into_affine().into_uncompressed();
let bytes = uncomp.as_ref();
@ -111,54 +104,52 @@ impl<E: Engine> Signature<E> {
}
/// A secret key, or a secret key share.
#[derive(Debug)]
pub struct SecretKey<E: Engine>(E::Fr);
#[derive(Debug, PartialEq, Eq)]
pub struct SecretKey(Fr);
impl<E: Engine> PartialEq for SecretKey<E> {
fn eq(&self, other: &SecretKey<E>) -> bool {
self.0 == other.0
}
}
impl<E: Engine> Default for SecretKey<E> {
impl Default for SecretKey {
fn default() -> Self {
SecretKey(E::Fr::zero())
SecretKey(Fr::zero())
}
}
impl<E: Engine> SecretKey<E> {
impl SecretKey {
/// Creates a new secret key.
pub fn new<R: Rng>(rng: &mut R) -> Self {
SecretKey(rng.gen())
}
/// Returns the matching public key.
pub fn public_key(&self) -> PublicKey<E> {
PublicKey(E::G1Affine::one().mul(self.0))
pub fn from_value(f: Fr) -> Self {
SecretKey(f)
}
/// Signs the given element of `E::G2`.
pub fn sign_g2<H: Into<E::G2Affine>>(&self, hash: H) -> Signature<E> {
/// Returns the matching public key.
pub fn public_key(&self) -> PublicKey {
PublicKey(G1Affine::one().mul(self.0))
}
/// Signs the given element of `G2`.
pub fn sign_g2<H: Into<G2Affine>>(&self, hash: H) -> Signature {
Signature(hash.into().mul(self.0))
}
/// Signs the given message.
pub fn sign<M: AsRef<[u8]>>(&self, msg: M) -> Signature<E> {
self.sign_g2(hash_g2::<E, M>(msg))
pub fn sign<M: AsRef<[u8]>>(&self, msg: M) -> Signature {
self.sign_g2(hash_g2(msg))
}
/// Returns the decrypted text, or `None`, if the ciphertext isn't valid.
pub fn decrypt(&self, ct: &Ciphertext<E>) -> Option<Vec<u8>> {
pub fn decrypt(&self, ct: &Ciphertext) -> Option<Vec<u8>> {
if !ct.verify() {
return None;
}
let Ciphertext(ref u, ref v, _) = *ct;
let g = u.into_affine().mul(self.0);
Some(xor_vec(&hash_bytes::<E>(g, v.len()), v))
Some(xor_vec(&hash_bytes(g, v.len()), v))
}
/// Returns a decryption share, or `None`, if the ciphertext isn't valid.
pub fn decrypt_share(&self, ct: &Ciphertext<E>) -> Option<DecryptionShare<E>> {
pub fn decrypt_share(&self, ct: &Ciphertext) -> Option<DecryptionShare> {
if !ct.verify() {
return None;
}
@ -167,20 +158,14 @@ impl<E: Engine> SecretKey<E> {
}
/// An encrypted message.
#[derive(Deserialize, Serialize, Debug)]
pub struct Ciphertext<E: Engine>(
#[serde(with = "serde_impl::projective")] E::G1,
#[derive(Deserialize, Serialize, Debug, Clone, PartialEq, Eq)]
pub struct Ciphertext(
#[serde(with = "serde_impl::projective")] G1,
Vec<u8>,
#[serde(with = "serde_impl::projective")] E::G2,
#[serde(with = "serde_impl::projective")] G2,
);
impl<E: Engine> PartialEq for Ciphertext<E> {
fn eq(&self, other: &Ciphertext<E>) -> bool {
self.0 == other.0 && self.1 == other.1 && self.2 == other.2
}
}
impl<E: Engine> Hash for Ciphertext<E> {
impl Hash for Ciphertext {
fn hash<H: Hasher>(&self, state: &mut H) {
let Ciphertext(ref u, ref v, ref w) = *self;
u.into_affine().into_compressed().as_ref().hash(state);
@ -189,47 +174,47 @@ impl<E: Engine> Hash for Ciphertext<E> {
}
}
impl<E: Engine> Ciphertext<E> {
impl Ciphertext {
/// Returns `true` if this is a valid ciphertext. This check is necessary to prevent
/// chosen-ciphertext attacks.
pub fn verify(&self) -> bool {
let Ciphertext(ref u, ref v, ref w) = *self;
let hash = hash_g1_g2::<E, _>(*u, v);
E::pairing(E::G1Affine::one(), *w) == E::pairing(*u, hash)
let hash = hash_g1_g2(*u, v);
Bls12::pairing(G1Affine::one(), *w) == Bls12::pairing(*u, hash)
}
}
/// A decryption share. A threshold of decryption shares can be used to decrypt a message.
#[derive(Deserialize, Serialize, Debug)]
pub struct DecryptionShare<E: Engine>(#[serde(with = "serde_impl::projective")] E::G1);
#[derive(Deserialize, Serialize, Debug, PartialEq, Eq)]
pub struct DecryptionShare(#[serde(with = "serde_impl::projective")] G1);
impl<E: Engine> PartialEq for DecryptionShare<E> {
fn eq(&self, other: &DecryptionShare<E>) -> bool {
self.0 == other.0
}
}
impl<E: Engine> Hash for DecryptionShare<E> {
impl Hash for DecryptionShare {
fn hash<H: Hasher>(&self, state: &mut H) {
self.0.into_affine().into_compressed().as_ref().hash(state);
}
}
/// A public key and an associated set of public key shares.
#[derive(Serialize, Deserialize, Clone, Debug, Hash)]
pub struct PublicKeySet<E: Engine> {
#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
pub struct PublicKeySet {
/// The coefficients of a polynomial whose value at `0` is the "master key", and value at
/// `i + 1` is key share number `i`.
commit: Commitment<E>,
commit: Commitment,
}
impl<E: Engine> From<Commitment<E>> for PublicKeySet<E> {
fn from(commit: Commitment<E>) -> PublicKeySet<E> {
impl Hash for PublicKeySet {
fn hash<H: Hasher>(&self, state: &mut H) {
self.commit.hash(state);
}
}
impl From<Commitment> for PublicKeySet {
fn from(commit: Commitment) -> PublicKeySet {
PublicKeySet { commit }
}
}
impl<E: Engine> PublicKeySet<E> {
impl PublicKeySet {
/// Returns the threshold `t`: any set of `t + 1` signature shares can be combined into a full
/// signature.
pub fn threshold(&self) -> usize {
@ -237,51 +222,51 @@ impl<E: Engine> PublicKeySet<E> {
}
/// Returns the public key.
pub fn public_key(&self) -> PublicKey<E> {
pub fn public_key(&self) -> PublicKey {
PublicKey(self.commit.evaluate(0))
}
/// Returns the `i`-th public key share.
pub fn public_key_share<T: Into<<E::Fr as PrimeField>::Repr>>(&self, i: T) -> PublicKey<E> {
PublicKey(self.commit.evaluate(from_repr_plus_1::<E::Fr>(i.into())))
pub fn public_key_share<T: Into<FrRepr>>(&self, i: T) -> PublicKey {
PublicKey(self.commit.evaluate(from_repr_plus_1::<Fr>(i.into())))
}
/// Combines the shares into a signature that can be verified with the main public key.
pub fn combine_signatures<'a, ITR, IND>(&self, shares: ITR) -> Result<Signature<E>>
pub fn combine_signatures<'a, ITR, IND>(&self, shares: ITR) -> Result<Signature>
where
ITR: IntoIterator<Item = (&'a IND, &'a Signature<E>)>,
IND: Into<<E::Fr as PrimeField>::Repr> + Clone + 'a,
ITR: IntoIterator<Item = (&'a IND, &'a Signature)>,
IND: Into<FrRepr> + Clone + 'a,
{
let samples = shares.into_iter().map(|(i, share)| (i, &share.0));
Ok(Signature(interpolate(self.commit.degree() + 1, samples)?))
}
/// Combines the shares to decrypt the ciphertext.
pub fn decrypt<'a, ITR, IND>(&self, shares: ITR, ct: &Ciphertext<E>) -> Result<Vec<u8>>
pub fn decrypt<'a, ITR, IND>(&self, shares: ITR, ct: &Ciphertext) -> Result<Vec<u8>>
where
ITR: IntoIterator<Item = (&'a IND, &'a DecryptionShare<E>)>,
IND: Into<<E::Fr as PrimeField>::Repr> + Clone + 'a,
ITR: IntoIterator<Item = (&'a IND, &'a DecryptionShare)>,
IND: Into<FrRepr> + Clone + 'a,
{
let samples = shares.into_iter().map(|(i, share)| (i, &share.0));
let g = interpolate(self.commit.degree() + 1, samples)?;
Ok(xor_vec(&hash_bytes::<E>(g, ct.1.len()), &ct.1))
Ok(xor_vec(&hash_bytes(g, ct.1.len()), &ct.1))
}
}
/// A secret key and an associated set of secret key shares.
pub struct SecretKeySet<E: Engine> {
pub struct SecretKeySet {
/// The coefficients of a polynomial whose value at `0` is the "master key", and value at
/// `i + 1` is key share number `i`.
poly: Poly<E>,
poly: Poly,
}
impl<E: Engine> From<Poly<E>> for SecretKeySet<E> {
fn from(poly: Poly<E>) -> SecretKeySet<E> {
impl From<Poly> for SecretKeySet {
fn from(poly: Poly) -> SecretKeySet {
SecretKeySet { poly }
}
}
impl<E: Engine> SecretKeySet<E> {
impl SecretKeySet {
/// Creates a set of secret key shares, where any `threshold + 1` of them can collaboratively
/// sign and decrypt.
pub fn random<R: Rng>(threshold: usize, rng: &mut R) -> Self {
@ -297,17 +282,14 @@ impl<E: Engine> SecretKeySet<E> {
}
/// Returns the `i`-th secret key share.
pub fn secret_key_share<T>(&self, i: T) -> ClearOnDrop<Box<SecretKey<E>>>
where
T: Into<<E::Fr as PrimeField>::Repr>,
{
pub fn secret_key_share<T: Into<FrRepr>>(&self, i: T) -> ClearOnDrop<Box<SecretKey>> {
ClearOnDrop::new(Box::new(SecretKey(
self.poly.evaluate(from_repr_plus_1::<E::Fr>(i.into())),
self.poly.evaluate(from_repr_plus_1::<Fr>(i.into())),
)))
}
/// Returns the corresponding public key set. That information can be shared publicly.
pub fn public_keys(&self) -> PublicKeySet<E> {
pub fn public_keys(&self) -> PublicKeySet {
PublicKeySet {
commit: self.poly.commitment(),
}
@ -315,13 +297,13 @@ impl<E: Engine> SecretKeySet<E> {
/// Returns the secret master key.
#[cfg(test)]
fn secret_key(&self) -> SecretKey<E> {
fn secret_key(&self) -> SecretKey {
SecretKey(self.poly.evaluate(0))
}
}
/// Returns a hash of the given message in `G2`.
fn hash_g2<E: Engine, M: AsRef<[u8]>>(msg: M) -> E::G2 {
fn hash_g2<M: AsRef<[u8]>>(msg: M) -> G2 {
let digest = digest::digest(&digest::SHA256, msg.as_ref());
let seed = <[u32; CHACHA_RNG_SEED_SIZE]>::init_with_indices(|i| {
BigEndian::read_u32(&digest.as_ref()[(4 * i)..(4 * i + 4)])
@ -331,7 +313,7 @@ fn hash_g2<E: Engine, M: AsRef<[u8]>>(msg: M) -> E::G2 {
}
/// Returns a hash of the group element and message, in the second group.
fn hash_g1_g2<E: Engine, M: AsRef<[u8]>>(g1: E::G1, msg: M) -> E::G2 {
fn hash_g1_g2<M: AsRef<[u8]>>(g1: G1, msg: M) -> G2 {
// If the message is large, hash it, otherwise copy it.
// TODO: Benchmark and optimize the threshold.
let mut msg = if msg.as_ref().len() > 64 {
@ -341,11 +323,11 @@ fn hash_g1_g2<E: Engine, M: AsRef<[u8]>>(g1: E::G1, msg: M) -> E::G2 {
msg.as_ref().to_vec()
};
msg.extend(g1.into_affine().into_compressed().as_ref());
hash_g2::<E, _>(&msg)
hash_g2(&msg)
}
/// Returns a hash of the group element with the specified length in bytes.
fn hash_bytes<E: Engine>(g1: E::G1, len: usize) -> Vec<u8> {
fn hash_bytes(g1: G1, len: usize) -> Vec<u8> {
let digest = digest::digest(&digest::SHA256, g1.into_affine().into_compressed().as_ref());
let seed = <[u32; CHACHA_RNG_SEED_SIZE]>::init_with_indices(|i| {
BigEndian::read_u32(&digest.as_ref()[(4 * i)..(4 * i + 4)])
@ -407,14 +389,13 @@ mod tests {
use std::collections::BTreeMap;
use pairing::bls12_381::Bls12;
use rand;
#[test]
fn test_simple_sig() {
let mut rng = rand::thread_rng();
let sk0 = SecretKey::<Bls12>::new(&mut rng);
let sk1 = SecretKey::<Bls12>::new(&mut rng);
let sk0 = SecretKey::new(&mut rng);
let sk1 = SecretKey::new(&mut rng);
let pk0 = sk0.public_key();
let msg0 = b"Real news";
let msg1 = b"Fake news";
@ -426,7 +407,7 @@ mod tests {
#[test]
fn test_threshold_sig() {
let mut rng = rand::thread_rng();
let sk_set = SecretKeySet::<Bls12>::random(3, &mut rng);
let sk_set = SecretKeySet::random(3, &mut rng);
let pk_set = sk_set.public_keys();
// Make sure the keys are different, and the first coefficient is the main key.
@ -449,7 +430,7 @@ mod tests {
// Each of the shares is a valid signature matching its public key share.
for (i, sig) in &sigs {
pk_set.public_key_share(*i).verify(sig, msg);
assert!(pk_set.public_key_share(*i).verify(sig, msg));
}
// Combined, they produce a signature matching the main public key.
@ -468,8 +449,8 @@ mod tests {
#[test]
fn test_simple_enc() {
let mut rng = rand::thread_rng();
let sk_bob = SecretKey::<Bls12>::new(&mut rng);
let sk_eve = SecretKey::<Bls12>::new(&mut rng);
let sk_bob = SecretKey::new(&mut rng);
let sk_eve = SecretKey::new(&mut rng);
let pk_bob = sk_bob.public_key();
let msg = b"Muffins in the canteen today! Don't tell Eve!";
let ciphertext = pk_bob.encrypt(&msg[..]);
@ -485,7 +466,7 @@ mod tests {
// Eve tries to trick Bob into decrypting `msg` xor `v`, but it doesn't validate.
let Ciphertext(u, v, w) = ciphertext;
let fake_ciphertext = Ciphertext::<Bls12>(u, vec![0; v.len()], w);
let fake_ciphertext = Ciphertext(u, vec![0; v.len()], w);
assert!(!fake_ciphertext.verify());
assert_eq!(None, sk_bob.decrypt(&fake_ciphertext));
}
@ -493,7 +474,7 @@ mod tests {
#[test]
fn test_threshold_enc() {
let mut rng = rand::thread_rng();
let sk_set = SecretKeySet::<Bls12>::random(3, &mut rng);
let sk_set = SecretKeySet::random(3, &mut rng);
let pk_set = sk_set.public_keys();
let msg = b"Totally real news";
let ciphertext = pk_set.public_key().encrypt(&msg[..]);
@ -530,10 +511,9 @@ mod tests {
let msg_end0: Vec<u8> = msg.iter().chain(b"end0").cloned().collect();
let msg_end1: Vec<u8> = msg.iter().chain(b"end1").cloned().collect();
let hash = hash_g2::<Bls12, _>;
assert_eq!(hash(&msg), hash(&msg));
assert_ne!(hash(&msg), hash(&msg_end0));
assert_ne!(hash(&msg_end0), hash(&msg_end1));
assert_eq!(hash_g2(&msg), hash_g2(&msg));
assert_ne!(hash_g2(&msg), hash_g2(&msg_end0));
assert_ne!(hash_g2(&msg_end0), hash_g2(&msg_end1));
}
/// Some basic sanity checks for the `hash_g1_g2` function.
@ -546,11 +526,10 @@ mod tests {
let g0 = rng.gen();
let g1 = rng.gen();
let hash = hash_g1_g2::<Bls12, _>;
assert_eq!(hash(g0, &msg), hash(g0, &msg));
assert_ne!(hash(g0, &msg), hash(g0, &msg_end0));
assert_ne!(hash(g0, &msg_end0), hash(g0, &msg_end1));
assert_ne!(hash(g0, &msg), hash(g1, &msg));
assert_eq!(hash_g1_g2(g0, &msg), hash_g1_g2(g0, &msg));
assert_ne!(hash_g1_g2(g0, &msg), hash_g1_g2(g0, &msg_end0));
assert_ne!(hash_g1_g2(g0, &msg_end0), hash_g1_g2(g0, &msg_end1));
assert_ne!(hash_g1_g2(g0, &msg), hash_g1_g2(g1, &msg));
}
/// Some basic sanity checks for the `hash_bytes` function.
@ -559,7 +538,7 @@ mod tests {
let mut rng = rand::thread_rng();
let g0 = rng.gen();
let g1 = rng.gen();
let hash = hash_bytes::<Bls12>;
let hash = hash_bytes;
assert_eq!(hash(g0, 5), hash(g0, 5));
assert_ne!(hash(g0, 5), hash(g1, 5));
assert_eq!(5, hash(g0, 5).len());
@ -572,7 +551,7 @@ mod tests {
use bincode;
let mut rng = rand::thread_rng();
let sk = SecretKey::<Bls12>::new(&mut rng);
let sk = SecretKey::new(&mut rng);
let sig = sk.sign("Please sign here: ______");
let pk = sk.public_key();
let ser_pk = bincode::serialize(&pk).expect("serialize public key");

215
src/crypto/poly.rs
View File

@ -1,48 +1,41 @@
//! Utilities for distributed key generation.
//! Utilities for distributed key generation: uni- and bivariate polynomials and commitments.
//!
//! A `BivarPoly` can be used for Verifiable Secret Sharing (VSS) and for key generation by a
//! trusted dealer. In a perfectly synchronous setting, e.g. on a blockchain or other agreed
//! transaction log, it works like this:
//! If `G` is a group of prime order `r` (written additively), and `g` is a generator, then
//! multiplication by integers factors through `r`, so the map `x -> x * g` (the sum of `x`
//! copies of `g`) is a homomorphism from the field `Fr` of integers modulo `r` to `G`. If the
//! _discrete logarithm_ is hard, i.e. it is infeasible to reverse this map, then `x * g` can be
//! considered a _commitment_ to `x`: By publishing it, you can guarantee to others that you won't
//! change your mind about the value `x`, without revealing it.
//!
//! The dealer generates a `BivarPoly` of degree `t` and publishes the `BivariateCommitment`,
//! with which the polynomial's values can be publicly verified. They then send _row_ `m > 0` to
//! node number `m`. Node `m`, in turn, sends _value_ `s` to node number `s`. Then if `2 * t + 1`
//! nodes confirm that they received a valid row, and there are at most `t` faulty nodes, then at
//! least `t + 1` honest nodes sent on an entry of every other node's column to that node. So we
//! know that every node can now reconstruct its column and the value at `0` of its column. These
//! values all lie on a univariate polynomial of degree `t`, so they can be used as secret keys.
//! This concept extends to polynomials: If you have a polynomial `f` over `Fr`, defined as
//! `a * X * X + b * X + c`, you can publish `a * g`, `b * g` and `c * g`. Then others will be able
//! to verify any single value `f(x)` of the polynomial without learning the original polynomial,
//! because `f(x) * g == x * x * (a * g) + x * (b * g) + (c * g)`. Only after learning three (in
//! general `degree + 1`) values, they can interpolate `f` itself.
//!
//! For Distributed Key Generation (DKG), every node proposes a polynomial via VSS. After a fixed
//! number (at least `N - 2 * t` if there are `N` nodes and up to `t` faulty ones) of them have
//! successfully been distributed, every node adds up the resulting secrets. Since the sum of
//! polynomials of degree `t` is itself a polynomial of degree `t`, these sums are still valid
//! secret keys, but now nobody knows the master key (number `0`).
// TODO: Expand this explanation and add examples, once the API is complete and stable.
//! This module defines univariate polynomials (in one variable) and _symmetric_ bivariate
//! polynomials (in two variables) over a field `Fr`, as well as their _commitments_ in `G`.
use std::borrow::Borrow;
use std::hash::{Hash, Hasher};
use std::{cmp, iter, ops};
use pairing::{CurveAffine, CurveProjective, Engine, Field, PrimeField};
use pairing::bls12_381::{Fr, FrRepr, G1, G1Affine};
use pairing::{CurveAffine, CurveProjective, Field, PrimeField};
use rand::Rng;
/// A univariate polynomial in the prime field.
#[derive(Clone, Debug)]
pub struct Poly<E: Engine> {
#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
pub struct Poly {
/// The coefficients of a polynomial.
coeff: Vec<E::Fr>,
#[serde(with = "super::serde_impl::field_vec")]
coeff: Vec<Fr>,
}
impl<E: Engine> PartialEq for Poly<E> {
fn eq(&self, other: &Self) -> bool {
self.coeff == other.coeff
}
}
impl<B: Borrow<Poly<E>>, E: Engine> ops::AddAssign<B> for Poly<E> {
impl<B: Borrow<Poly>> ops::AddAssign<B> for Poly {
fn add_assign(&mut self, rhs: B) {
let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len());
self.coeff.resize(len, E::Fr::zero());
self.coeff.resize(len, Fr::zero());
for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) {
self_c.add_assign(rhs_c);
}
@ -50,27 +43,27 @@ impl<B: Borrow<Poly<E>>, E: Engine> ops::AddAssign<B> for Poly<E> {
}
}
impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Add<B> for &'a Poly<E> {
type Output = Poly<E>;
impl<'a, B: Borrow<Poly>> ops::Add<B> for &'a Poly {
type Output = Poly;
fn add(self, rhs: B) -> Poly<E> {
fn add(self, rhs: B) -> Poly {
(*self).clone() + rhs
}
}
impl<B: Borrow<Poly<E>>, E: Engine> ops::Add<B> for Poly<E> {
type Output = Poly<E>;
impl<B: Borrow<Poly>> ops::Add<B> for Poly {
type Output = Poly;
fn add(mut self, rhs: B) -> Poly<E> {
fn add(mut self, rhs: B) -> Poly {
self += rhs;
self
}
}
impl<B: Borrow<Poly<E>>, E: Engine> ops::SubAssign<B> for Poly<E> {
impl<B: Borrow<Poly>> ops::SubAssign<B> for Poly {
fn sub_assign(&mut self, rhs: B) {
let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len());
self.coeff.resize(len, E::Fr::zero());
self.coeff.resize(len, Fr::zero());
for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) {
self_c.sub_assign(rhs_c);
}
@ -78,18 +71,18 @@ impl<B: Borrow<Poly<E>>, E: Engine> ops::SubAssign<B> for Poly<E> {
}
}
impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Sub<B> for &'a Poly<E> {
type Output = Poly<E>;
impl<'a, B: Borrow<Poly>> ops::Sub<B> for &'a Poly {
type Output = Poly;
fn sub(self, rhs: B) -> Poly<E> {
fn sub(self, rhs: B) -> Poly {
(*self).clone() - rhs
}
}
impl<B: Borrow<Poly<E>>, E: Engine> ops::Sub<B> for Poly<E> {
type Output = Poly<E>;
impl<B: Borrow<Poly>> ops::Sub<B> for Poly {
type Output = Poly;
fn sub(mut self, rhs: B) -> Poly<E> {
fn sub(mut self, rhs: B) -> Poly {
self -= rhs;
self
}
@ -97,13 +90,13 @@ impl<B: Borrow<Poly<E>>, E: Engine> ops::Sub<B> for Poly<E> {
// Clippy thinks using any `+` and `-` in a `Mul` implementation is suspicious.
#[cfg_attr(feature = "cargo-clippy", allow(suspicious_arithmetic_impl))]
impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Mul<B> for &'a Poly<E> {
type Output = Poly<E>;
impl<'a, B: Borrow<Poly>> ops::Mul<B> for &'a Poly {
type Output = Poly;
fn mul(self, rhs: B) -> Self::Output {
let coeff = (0..(self.coeff.len() + rhs.borrow().coeff.len() - 1))
.map(|i| {
let mut c = E::Fr::zero();
let mut c = Fr::zero();
for j in i.saturating_sub(rhs.borrow().degree())..(1 + cmp::min(i, self.degree())) {
let mut s = self.coeff[j];
s.mul_assign(&rhs.borrow().coeff[i - j]);
@ -116,21 +109,21 @@ impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Mul<B> for &'a Poly<E> {
}
}
impl<B: Borrow<Poly<E>>, E: Engine> ops::Mul<B> for Poly<E> {
type Output = Poly<E>;
impl<B: Borrow<Poly>> ops::Mul<B> for Poly {
type Output = Poly;
fn mul(self, rhs: B) -> Self::Output {
&self * rhs
}
}
impl<B: Borrow<Self>, E: Engine> ops::MulAssign<B> for Poly<E> {
impl<B: Borrow<Self>> ops::MulAssign<B> for Poly {
fn mul_assign(&mut self, rhs: B) {
*self = &*self * rhs;
}
}
impl<E: Engine> Poly<E> {
impl Poly {
/// Creates a random polynomial.
pub fn random<R: Rng>(degree: usize, rng: &mut R) -> Self {
Poly {
@ -149,7 +142,7 @@ impl<E: Engine> Poly<E> {
}
/// Returns the polynomial with constant value `c`.
pub fn constant(c: E::Fr) -> Self {
pub fn constant(c: Fr) -> Self {
Poly { coeff: vec![c] }
}
@ -161,9 +154,9 @@ impl<E: Engine> Poly<E> {
/// Returns the (monic) monomial "`x.pow(degree)`".
pub fn monomial(degree: usize) -> Self {
Poly {
coeff: iter::repeat(E::Fr::zero())
coeff: iter::repeat(Fr::zero())
.take(degree)
.chain(iter::once(E::Fr::one()))
.chain(iter::once(Fr::one()))
.collect(),
}
}
@ -172,14 +165,14 @@ impl<E: Engine> Poly<E> {
/// `(x, f(x))`.
pub fn interpolate<'a, T, I>(samples_repr: I) -> Self
where
I: IntoIterator<Item = (&'a T, &'a E::Fr)>,
T: Into<<E::Fr as PrimeField>::Repr> + Clone + 'a,
I: IntoIterator<Item = (&'a T, &'a Fr)>,
T: Into<FrRepr> + Clone + 'a,
{
let convert = |(x_repr, y): (&T, &E::Fr)| {
let x = E::Fr::from_repr(x_repr.clone().into()).expect("invalid index");
let convert = |(x_repr, y): (&T, &Fr)| {
let x = Fr::from_repr(x_repr.clone().into()).expect("invalid index");
(x, *y)
};
let samples: Vec<(E::Fr, E::Fr)> = samples_repr.into_iter().map(convert).collect();
let samples: Vec<(Fr, Fr)> = samples_repr.into_iter().map(convert).collect();
Self::compute_interpolation(&samples)
}
@ -189,12 +182,12 @@ impl<E: Engine> Poly<E> {
}
/// Returns the value at the point `i`.
pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, i: T) -> E::Fr {
pub fn evaluate<T: Into<FrRepr>>(&self, i: T) -> Fr {
let mut result = match self.coeff.last() {
None => return E::Fr::zero(),
None => return Fr::zero(),
Some(c) => *c,
};
let x = E::Fr::from_repr(i.into()).expect("invalid index");
let x = Fr::from_repr(i.into()).expect("invalid index");
for c in self.coeff.iter().rev().skip(1) {
result.mul_assign(&x);
result.add_assign(c);
@ -203,8 +196,8 @@ impl<E: Engine> Poly<E> {
}
/// Returns the corresponding commitment.
pub fn commitment(&self) -> Commitment<E> {
let to_g1 = |c: &E::Fr| E::G1Affine::one().mul(*c);
pub fn commitment(&self) -> Commitment {
let to_g1 = |c: &Fr| G1Affine::one().mul(*c);
Commitment {
coeff: self.coeff.iter().map(to_g1).collect(),
}
@ -219,7 +212,7 @@ impl<E: Engine> Poly<E> {
/// Returns the unique polynomial `f` of degree `samples.len() - 1` with the given values
/// `(x, f(x))`.
fn compute_interpolation(samples: &[(E::Fr, E::Fr)]) -> Self {
fn compute_interpolation(samples: &[(Fr, Fr)]) -> Self {
if samples.is_empty() {
return Poly::zero();
} else if samples.len() == 1 {
@ -236,7 +229,7 @@ impl<E: Engine> Poly<E> {
}
/// Returns the Lagrange base polynomial that is `1` in `p` and `0` in every `samples[i].0`.
fn lagrange(p: E::Fr, samples: &[(E::Fr, E::Fr)]) -> Self {
fn lagrange(p: Fr, samples: &[(Fr, Fr)]) -> Self {
let mut result = Self::one();
for &(sx, _) in samples {
let mut denom = p;
@ -249,20 +242,14 @@ impl<E: Engine> Poly<E> {
}
/// A commitment to a univariate polynomial.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Commitment<E: Engine> {
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct Commitment {
/// The coefficients of the polynomial.
#[serde(with = "super::serde_impl::projective_vec")]
coeff: Vec<E::G1>,
coeff: Vec<G1>,
}
impl<E: Engine> PartialEq for Commitment<E> {
fn eq(&self, other: &Self) -> bool {
self.coeff == other.coeff
}
}
impl<E: Engine> Hash for Commitment<E> {
impl Hash for Commitment {
fn hash<H: Hasher>(&self, state: &mut H) {
self.coeff.len().hash(state);
for c in &self.coeff {
@ -271,10 +258,10 @@ impl<E: Engine> Hash for Commitment<E> {
}
}
impl<B: Borrow<Commitment<E>>, E: Engine> ops::AddAssign<B> for Commitment<E> {
impl<B: Borrow<Commitment>> ops::AddAssign<B> for Commitment {
fn add_assign(&mut self, rhs: B) {
let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len());
self.coeff.resize(len, E::G1::zero());
self.coeff.resize(len, G1::zero());
for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) {
self_c.add_assign(rhs_c);
}
@ -282,36 +269,36 @@ impl<B: Borrow<Commitment<E>>, E: Engine> ops::AddAssign<B> for Commitment<E> {
}
}
impl<'a, B: Borrow<Commitment<E>>, E: Engine> ops::Add<B> for &'a Commitment<E> {
type Output = Commitment<E>;
impl<'a, B: Borrow<Commitment>> ops::Add<B> for &'a Commitment {
type Output = Commitment;
fn add(self, rhs: B) -> Commitment<E> {
fn add(self, rhs: B) -> Commitment {
(*self).clone() + rhs
}
}
impl<B: Borrow<Commitment<E>>, E: Engine> ops::Add<B> for Commitment<E> {
type Output = Commitment<E>;
impl<B: Borrow<Commitment>> ops::Add<B> for Commitment {
type Output = Commitment;
fn add(mut self, rhs: B) -> Commitment<E> {
fn add(mut self, rhs: B) -> Commitment {
self += rhs;
self
}
}
impl<E: Engine> Commitment<E> {
impl Commitment {
/// Returns the polynomial's degree.
pub fn degree(&self) -> usize {
self.coeff.len() - 1
}
/// Returns the `i`-th public key share.
pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, i: T) -> E::G1 {
pub fn evaluate<T: Into<FrRepr>>(&self, i: T) -> G1 {
let mut result = match self.coeff.last() {
None => return E::G1::zero(),
None => return G1::zero(),
Some(c) => *c,
};
let x = E::Fr::from_repr(i.into()).expect("invalid index");
let x = Fr::from_repr(i.into()).expect("invalid index");
for c in self.coeff.iter().rev().skip(1) {
result.mul_assign(x);
result.add_assign(c);
@ -332,15 +319,15 @@ impl<E: Engine> Commitment<E> {
/// This can be used for Verifiable Secret Sharing and Distributed Key Generation. See the module
/// documentation for details.
#[derive(Debug, Clone)]
pub struct BivarPoly<E: Engine> {
pub struct BivarPoly {
/// The polynomial's degree in each of the two variables.
degree: usize,
/// The coefficients of the polynomial. Coefficient `(i, j)` for `i <= j` is in position
/// `j * (j + 1) / 2 + i`.
coeff: Vec<E::Fr>,
coeff: Vec<Fr>,
}
impl<E: Engine> BivarPoly<E> {
impl BivarPoly {
/// Creates a random polynomial.
pub fn random<R: Rng>(degree: usize, rng: &mut R) -> Self {
BivarPoly {
@ -355,11 +342,11 @@ impl<E: Engine> BivarPoly<E> {
}
/// Returns the polynomial's value at the point `(x, y)`.
pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T, y: T) -> E::Fr {
pub fn evaluate<T: Into<FrRepr>>(&self, x: T, y: T) -> Fr {
let x_pow = self.powers(x);
let y_pow = self.powers(y);
// TODO: Can we save a few multiplication steps here due to the symmetry?
let mut result = E::Fr::zero();
let mut result = Fr::zero();
for (i, x_pow_i) in x_pow.into_iter().enumerate() {
for (j, y_pow_j) in y_pow.iter().enumerate() {
let mut summand = self.coeff[coeff_pos(i, j)];
@ -372,11 +359,11 @@ impl<E: Engine> BivarPoly<E> {
}
/// Returns the `x`-th row, as a univariate polynomial.
pub fn row<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T) -> Poly<E> {
pub fn row<T: Into<FrRepr>>(&self, x: T) -> Poly {
let x_pow = self.powers(x);
let coeff: Vec<E::Fr> = (0..=self.degree)
let coeff: Vec<Fr> = (0..=self.degree)
.map(|i| {
let mut result = E::Fr::zero();
let mut result = Fr::zero();
for (j, x_pow_j) in x_pow.iter().enumerate() {
let mut summand = self.coeff[coeff_pos(i, j)];
summand.mul_assign(x_pow_j);
@ -389,8 +376,8 @@ impl<E: Engine> BivarPoly<E> {
}
/// Returns the corresponding commitment. That information can be shared publicly.
pub fn commitment(&self) -> BivarCommitment<E> {
let to_pub = |c: &E::Fr| E::G1Affine::one().mul(*c);
pub fn commitment(&self) -> BivarCommitment {
let to_pub = |c: &Fr| G1Affine::one().mul(*c);
BivarCommitment {
degree: self.degree,
coeff: self.coeff.iter().map(to_pub).collect(),
@ -398,22 +385,22 @@ impl<E: Engine> BivarPoly<E> {
}
/// Returns the `0`-th to `degree`-th power of `x`.
fn powers<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x_repr: T) -> Vec<E::Fr> {
fn powers<T: Into<FrRepr>>(&self, x_repr: T) -> Vec<Fr> {
powers(x_repr, self.degree)
}
}
/// A commitment to a bivariate polynomial.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BivarCommitment<E: Engine> {
pub struct BivarCommitment {
/// The polynomial's degree in each of the two variables.
degree: usize,
/// The commitments to the coefficients.
#[serde(with = "super::serde_impl::projective_vec")]
coeff: Vec<E::G1>,
coeff: Vec<G1>,
}
impl<E: Engine> Hash for BivarCommitment<E> {
impl Hash for BivarCommitment {
fn hash<H: Hasher>(&self, state: &mut H) {
self.degree.hash(state);
for c in &self.coeff {
@ -422,18 +409,18 @@ impl<E: Engine> Hash for BivarCommitment<E> {
}
}
impl<E: Engine> BivarCommitment<E> {
impl BivarCommitment {
/// Returns the polynomial's degree: It is the same in both variables.
pub fn degree(&self) -> usize {
self.degree
}
/// Returns the commitment's value at the point `(x, y)`.
pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T, y: T) -> E::G1 {
pub fn evaluate<T: Into<FrRepr>>(&self, x: T, y: T) -> G1 {
let x_pow = self.powers(x);
let y_pow = self.powers(y);
// TODO: Can we save a few multiplication steps here due to the symmetry?
let mut result = E::G1::zero();
let mut result = G1::zero();
for (i, x_pow_i) in x_pow.into_iter().enumerate() {
for (j, y_pow_j) in y_pow.iter().enumerate() {
let mut summand = self.coeff[coeff_pos(i, j)];
@ -446,11 +433,11 @@ impl<E: Engine> BivarCommitment<E> {
}
/// Returns the `x`-th row, as a commitment to a univariate polynomial.
pub fn row<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T) -> Commitment<E> {
pub fn row<T: Into<FrRepr>>(&self, x: T) -> Commitment {
let x_pow = self.powers(x);
let coeff: Vec<E::G1> = (0..=self.degree)
let coeff: Vec<G1> = (0..=self.degree)
.map(|i| {
let mut result = E::G1::zero();
let mut result = G1::zero();
for (j, x_pow_j) in x_pow.iter().enumerate() {
let mut summand = self.coeff[coeff_pos(i, j)];
summand.mul_assign(*x_pow_j);
@ -463,7 +450,7 @@ impl<E: Engine> BivarCommitment<E> {
}
/// Returns the `0`-th to `degree`-th power of `x`.
fn powers<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x_repr: T) -> Vec<E::Fr> {
fn powers<T: Into<FrRepr>>(&self, x_repr: T) -> Vec<Fr> {
powers(x_repr, self.degree)
}
}
@ -497,12 +484,10 @@ mod tests {
use super::{coeff_pos, BivarPoly, Poly};
use pairing::bls12_381::Bls12;
use pairing::{CurveAffine, Engine, Field, PrimeField};
use pairing::bls12_381::{Fr, G1Affine};
use pairing::{CurveAffine, Field, PrimeField};
use rand;
type Fr = <Bls12 as Engine>::Fr;
fn fr(x: i64) -> Fr {
let mut result = Fr::from_repr((x.abs() as u64).into()).unwrap();
if x < 0 {
@ -529,7 +514,7 @@ mod tests {
#[test]
fn poly() {
// The polynomial "`5 * x.pow(3) + x.pow(1) - 2`".
let poly: Poly<Bls12> =
let poly =
Poly::monomial(3) * Poly::constant(fr(5)) + Poly::monomial(1) - Poly::constant(fr(2));
let coeff = vec![fr(-2), fr(1), fr(0), fr(5)];
assert_eq!(Poly { coeff }, poly);
@ -556,7 +541,7 @@ mod tests {
// For distributed key generation, a number of dealers, only one of who needs to be honest,
// generates random bivariate polynomials and publicly commits to them. In partice, the
// dealers can e.g. be any `faulty_num + 1` nodes.
let bi_polys: Vec<BivarPoly<Bls12>> = (0..dealer_num)
let bi_polys: Vec<BivarPoly> = (0..dealer_num)
.map(|_| BivarPoly::random(faulty_num, &mut rng))
.collect();
let pub_bi_commits: Vec<_> = bi_polys.iter().map(BivarPoly::commitment).collect();
@ -575,7 +560,7 @@ mod tests {
// Node `s` receives the `s`-th value and verifies it.
for s in 1..=node_num {
let val = row_poly.evaluate(s as u64);
let val_g1 = <Bls12 as Engine>::G1Affine::one().mul(val);
let val_g1 = G1Affine::one().mul(val);
assert_eq!(bi_commit.evaluate(m as u64, s as u64), val_g1);
// The node can't verify this directly, but it should have the correct value:
assert_eq!(bi_poly.evaluate(m as u64, s as u64), val);

7
src/crypto/protobuf_impl.rs
View File

@ -1,14 +1,15 @@
use super::Signature;
use pairing::{CurveAffine, CurveProjective, EncodedPoint, Engine};
use pairing::bls12_381::G2Compressed;
use pairing::{CurveAffine, CurveProjective, EncodedPoint};
impl<E: Engine> Signature<E> {
impl Signature {
pub fn to_vec(&self) -> Vec<u8> {
let comp = self.0.into_affine().into_compressed();
comp.as_ref().to_vec()
}
pub fn from_bytes(bytes: &[u8]) -> Option<Self> {
let mut comp = <E::G2Affine as CurveAffine>::Compressed::empty();
let mut comp = G2Compressed::empty();
comp.as_mut().copy_from_slice(bytes);
if let Ok(affine) = comp.into_affine() {
Some(Signature(affine.into_projective()))

102
src/crypto/serde_impl.rs
View File

@ -80,3 +80,105 @@ pub mod projective_vec {
Ok(wrap_vec.into_iter().map(|CurveWrap(c, _)| c).collect())
}
}
/// Serialization and deserialization of vectors of field elements.
pub mod field_vec {
use std::borrow::Borrow;
use std::marker::PhantomData;
use pairing::{PrimeField, PrimeFieldRepr};
use serde::de::Error as DeserializeError;
use serde::ser::Error as SerializeError;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
/// A wrapper type to facilitate serialization and deserialization of field elements.
pub struct FieldWrap<F, B>(B, PhantomData<F>);
impl<F, B> FieldWrap<F, B> {
pub fn new(f: B) -> Self {
FieldWrap(f, PhantomData)
}
}
impl<F> FieldWrap<F, F> {
pub fn into_inner(self) -> F {
self.0
}
}
impl<F: PrimeField, B: Borrow<F>> Serialize for FieldWrap<F, B> {
fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
let mut bytes = Vec::new();
self.0
.borrow()
.into_repr()
.write_be(&mut bytes)
.map_err(|_| S::Error::custom("failed to write bytes"))?;
bytes.serialize(s)
}
}
impl<'de, F: PrimeField> Deserialize<'de> for FieldWrap<F, F> {
fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
let bytes: Vec<u8> = Deserialize::deserialize(d)?;
let mut repr = F::zero().into_repr();
repr.read_be(&bytes[..])
.map_err(|_| D::Error::custom("failed to write bytes"))?;
Ok(FieldWrap::new(F::from_repr(repr).map_err(|_| {
D::Error::custom("invalid field element representation")
})?))
}
}
pub fn serialize<S, F>(vec: &[F], s: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
F: PrimeField,
{
let wrap_vec: Vec<FieldWrap<F, &F>> = vec.iter().map(FieldWrap::new).collect();
wrap_vec.serialize(s)
}
pub fn deserialize<'de, D, F>(d: D) -> Result<Vec<F>, D::Error>
where
D: Deserializer<'de>,
F: PrimeField,
{
let wrap_vec = <Vec<FieldWrap<F, F>>>::deserialize(d)?;
Ok(wrap_vec.into_iter().map(|FieldWrap(f, _)| f).collect())
}
}
#[cfg(test)]
mod tests {
use bincode;
use pairing::bls12_381::Bls12;
use pairing::Engine;
use rand::{self, Rng};
#[derive(Debug, Serialize, Deserialize)]
pub struct Vecs<E: Engine> {
#[serde(with = "super::projective_vec")]
curve_points: Vec<E::G1>,
#[serde(with = "super::field_vec")]
field_elements: Vec<E::Fr>,
}
impl<E: Engine> PartialEq for Vecs<E> {
fn eq(&self, other: &Self) -> bool {
self.curve_points == other.curve_points && self.field_elements == other.field_elements
}
}
#[test]
fn vecs() {
let mut rng = rand::thread_rng();
let vecs: Vecs<Bls12> = Vecs {
curve_points: rng.gen_iter().take(10).collect(),
field_elements: rng.gen_iter().take(10).collect(),
};
let ser_vecs = bincode::serialize(&vecs).expect("serialize vecs");
let de_vecs = bincode::deserialize(&ser_vecs).expect("deserialize vecs");
assert_eq!(vecs, de_vecs);
}
}

1
src/lib.rs
View File

@ -127,3 +127,4 @@ pub mod messaging;
pub mod proto;
#[cfg(feature = "serialization-protobuf")]
pub mod proto_io;
pub mod sync_key_gen;

13
src/messaging.rs
View File

@ -2,7 +2,6 @@ use std::collections::{BTreeMap, BTreeSet};
use std::fmt::Debug;
use clear_on_drop::ClearOnDrop;
use pairing::bls12_381::Bls12;
use crypto::{PublicKeySet, SecretKey};
@ -143,8 +142,8 @@ pub struct NetworkInfo<NodeUid> {
all_uids: BTreeSet<NodeUid>,
num_nodes: usize,
num_faulty: usize,
secret_key: ClearOnDrop<Box<SecretKey<Bls12>>>,
public_key_set: PublicKeySet<Bls12>,
secret_key: ClearOnDrop<Box<SecretKey>>,
public_key_set: PublicKeySet,
node_indices: BTreeMap<NodeUid, usize>,
}
@ -152,8 +151,8 @@ impl<NodeUid: Clone + Ord> NetworkInfo<NodeUid> {
pub fn new(
our_uid: NodeUid,
all_uids: BTreeSet<NodeUid>,
secret_key: ClearOnDrop<Box<SecretKey<Bls12>>>,
public_key_set: PublicKeySet<Bls12>,
secret_key: ClearOnDrop<Box<SecretKey>>,
public_key_set: PublicKeySet,
) -> Self {
if !all_uids.contains(&our_uid) {
panic!("Missing own ID");
@ -197,11 +196,11 @@ impl<NodeUid: Clone + Ord> NetworkInfo<NodeUid> {
self.num_faulty
}
pub fn secret_key(&self) -> &SecretKey<Bls12> {
pub fn secret_key(&self) -> &SecretKey {
&self.secret_key
}
pub fn public_key_set(&self) -> &PublicKeySet<Bls12> {
pub fn public_key_set(&self) -> &PublicKeySet {
&self.public_key_set
}

241
src/sync_key_gen.rs Normal file
View File

@ -0,0 +1,241 @@
//! A _synchronous_ algorithm for dealerless distributed key generation.
//!
//! This protocol is meant to run in a _completely synchronous_ setting where each node handles all
//! messages in the same order. It can e.g. exchange messages as transactions on top of
//! `HoneyBadger`, or it can run "on-chain", i.e. committing its messages to a blockchain.
//!
//! Its messages are encrypted where necessary, so they can be publicly broadcast.
//!
//! When the protocol completes, every node receives a secret key share suitable for threshold
//! signatures and encryption. The secret master key is not known by anyone. The protocol succeeds
//! if up to `threshold` nodes are faulty.
//!
//! # How it works
//!
//! The algorithm is based on ideas from
//! [Distributed Key Generation in the Wild](https://eprint.iacr.org/2012/377.pdf) and
//! [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).
//!
//! In a trusted dealer scenario, the following steps occur:
//!
//! 1. Dealer generates a `BivarPoly` of degree `t` and publishes the `BivarCommitment` which is
//! used to publicly verify the polynomial's values.
//! 2. Dealer sends _row_ `m > 0` to node number `m`.
//! 3. Node `m`, in turn, sends _value_ `s` to node number `s`.
//! 4. This process continues until `2 * t + 1` nodes confirm they have received a valid row. If
//! there are at most `t` faulty nodes, we know that at least `t + 1` correct nodes sent on an
//! entry of every other node’s column to that node.
//! 5. This means every node can reconstruct its column, and the value at `0` of its column.
//! 6. These values all lie on a univariate polynomial of degree `t` and can be used as secret keys.
//!
//! In our _dealerless_ environment, at least `t + 1` nodes each generate a polynomial using the
//! method above. The sum of the secret keys we received from each node is then used as our secret
//! key. No single node knows the secret master key.
use std::collections::btree_map::Entry;
use std::collections::{BTreeMap, BTreeSet};
use crypto::poly::{BivarCommitment, BivarPoly, Poly};
use crypto::serde_impl::field_vec::FieldWrap;
use crypto::{Ciphertext, PublicKey, PublicKeySet, SecretKey};
use bincode;
use pairing::bls12_381::{Fr, G1Affine};
use pairing::{CurveAffine, Field};
use rand::OsRng;
// TODO: No need to send our own row and value to ourselves.
/// A commitment to a bivariate polynomial, and for each node, an encrypted row of values.
#[derive(Deserialize, Serialize, Debug, Clone)]
pub struct Propose(BivarCommitment, Vec<Ciphertext>);
/// A confirmation that we have received a node's proposal and verified our row against the
/// commitment. For each node, it contains one encrypted value of our row.
#[derive(Deserialize, Serialize, Debug, Clone)]
pub struct Accept(u64, Vec<Ciphertext>);
/// The information needed to track a single proposer's secret sharing process.
struct ProposalState {
/// The proposer's commitment.
commit: BivarCommitment,
/// The verified values we received from `Accept` messages.
values: BTreeMap<u64, Fr>,
/// The nodes which have accepted this proposal, valid or not.
accepts: BTreeSet<u64>,
}
impl ProposalState {
/// Creates a new proposal state with a commitment.
fn new(commit: BivarCommitment) -> ProposalState {
ProposalState {
commit,
values: BTreeMap::new(),
accepts: BTreeSet::new(),
}
}
/// Returns `true` if at least `2 * threshold + 1` nodes have accepted.
fn is_complete(&self, threshold: usize) -> bool {
self.accepts.len() > 2 * threshold
}
}
/// A synchronous algorithm for dealerless distributed key generation.
///
/// It requires that all nodes handle all messages in the exact same order.
pub struct SyncKeyGen {
/// Our node index.
our_idx: u64,
/// Our secret key.
sec_key: SecretKey,
/// The public keys of all nodes, by node index.
pub_keys: Vec<PublicKey>,
/// Proposed bivariate polynomial.
proposals: BTreeMap<u64, ProposalState>,
/// The degree of the generated polynomial.
threshold: usize,
}
impl SyncKeyGen {
/// Creates a new `SyncKeyGen` instance, together with the `Propose` message that should be
/// broadcast.
pub fn new(
our_idx: u64,
sec_key: SecretKey,
pub_keys: Vec<PublicKey>,
threshold: usize,
) -> (SyncKeyGen, Propose) {
let mut rng = OsRng::new().expect("OS random number generator");
let our_proposal = BivarPoly::random(threshold, &mut rng);
let commit = our_proposal.commitment();
let rows: Vec<_> = pub_keys
.iter()
.enumerate()
.map(|(i, pk)| {
let row = our_proposal.row(i as u64 + 1);
let bytes = bincode::serialize(&row).expect("failed to serialize row");
pk.encrypt(&bytes)
})
.collect();
let key_gen = SyncKeyGen {
our_idx,
sec_key,
pub_keys,
proposals: BTreeMap::new(),
threshold,
};
(key_gen, Propose(commit, rows))
}
/// Handles a `Propose` message. If it is valid, returns an `Accept` message to be broadcast.
pub fn handle_propose(
&mut self,
sender_idx: u64,
Propose(commit, rows): Propose,
) -> Option<Accept> {
let commit_row = commit.row(self.our_idx + 1);
match self.proposals.entry(sender_idx) {
Entry::Occupied(_) => return None, // Ignore multiple proposals.
Entry::Vacant(entry) => {
entry.insert(ProposalState::new(commit));
}
}
let ser_row = self.sec_key.decrypt(rows.get(self.our_idx as usize)?)?;
let row: Poly = bincode::deserialize(&ser_row).ok()?; // Ignore invalid messages.
if row.commitment() != commit_row {
debug!("Invalid proposal from node {}.", sender_idx);
return None;
}
// The row is valid: now encrypt one value for each node.
let values = self
.pub_keys
.iter()
.enumerate()
.map(|(idx, pk)| {
let val = row.evaluate(idx as u64 + 1);
let ser_val =
bincode::serialize(&FieldWrap::new(val)).expect("failed to serialize value");
pk.encrypt(ser_val)
})
.collect();
Some(Accept(sender_idx, values))
}
/// Handles an `Accept` message.
pub fn handle_accept(&mut self, sender_idx: u64, accept: Accept) {
if let Err(err) = self.handle_accept_or_err(sender_idx, accept) {
debug!("Invalid accept from node {}: {}", sender_idx, err);
}
}
/// Returns the number of complete proposals. 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.proposals
.values()
.filter(|proposal| proposal.is_complete(self.threshold))
.count()
}
/// Returns `true` if the proposal of the given node is complete.
pub fn is_node_ready(&self, proposer_idx: u64) -> bool {
self.proposals
.get(&proposer_idx)
.map_or(false, |proposal| proposal.is_complete(self.threshold))
}
/// Returns `true` if enough proposals are complete to safely generate the new key.
pub fn is_ready(&self) -> bool {
self.count_complete() > self.threshold
}
/// Returns the new secret key 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.
pub fn generate(&self) -> (PublicKeySet, SecretKey) {
let mut pk_commit = Poly::zero().commitment();
let mut sk_val = Fr::zero();
for proposal in self
.proposals
.values()
.filter(|proposal| proposal.is_complete(self.threshold))
{
pk_commit += proposal.commit.row(0);
let row: Poly = Poly::interpolate(proposal.values.iter().take(self.threshold + 1));
sk_val.add_assign(&row.evaluate(0));
}
(pk_commit.into(), SecretKey::from_value(sk_val))
}
/// Handles an `Accept` message or returns an error string.
fn handle_accept_or_err(
&mut self,
sender_idx: u64,
Accept(proposer_idx, values): Accept,
) -> Result<(), String> {
let proposal = self
.proposals
.get_mut(&proposer_idx)
.ok_or_else(|| "sender does not exist".to_string())?;
if !proposal.accepts.insert(sender_idx) {
return Err("duplicate accept".to_string());
}
if values.len() != self.pub_keys.len() {
return Err("wrong node count".to_string());
}
let ser_val: Vec<u8> = self
.sec_key
.decrypt(&values[self.our_idx as usize])
.ok_or_else(|| "value decryption failed".to_string())?;
let val = bincode::deserialize::<FieldWrap<Fr, Fr>>(&ser_val)
.map_err(|err| format!("deserialization failed: {:?}", err))?
.into_inner();
if proposal.commit.evaluate(self.our_idx + 1, sender_idx + 1) != G1Affine::one().mul(val) {
return Err("wrong value".to_string());
}
proposal.values.insert(sender_idx + 1, val);
Ok(())
}
}

3
tests/broadcast.rs
View File

@ -13,7 +13,6 @@ use std::collections::{BTreeMap, BTreeSet};
use std::iter::once;
use std::rc::Rc;
use pairing::bls12_381::Bls12;
use rand::Rng;
use hbbft::broadcast::{Broadcast, BroadcastMessage};
@ -72,7 +71,7 @@ impl Adversary<Broadcast<NodeUid>> for ProposeAdversary {
// FIXME: Take the correct, known keys from the network.
let mut rng = rand::thread_rng();
let sk_set = SecretKeySet::<Bls12>::random(self.adv_nodes.len(), &mut rng);
let sk_set = SecretKeySet::random(self.adv_nodes.len(), &mut rng);
let pk_set = sk_set.public_keys();
let netinfo = Rc::new(NetworkInfo::new(

3
tests/network/mod.rs
View File

@ -3,7 +3,6 @@ use std::fmt::Debug;
use std::hash::Hash;
use std::rc::Rc;
use pairing::bls12_381::Bls12;
use rand::{self, Rng};
use hbbft::crypto::SecretKeySet;
@ -164,7 +163,7 @@ where
F: Fn(Rc<NetworkInfo<NodeUid>>) -> D,
{
let mut rng = rand::thread_rng();
let sk_set = SecretKeySet::<Bls12>::random(adv_num, &mut rng);
let sk_set = SecretKeySet::random(adv_num, &mut rng);
let pk_set = sk_set.public_keys();
let node_ids: BTreeSet<NodeUid> = (0..(good_num + adv_num)).map(NodeUid).collect();

85
tests/sync_key_gen.rs Normal file
View File

@ -0,0 +1,85 @@
//! Tests for synchronous distributed key generation.
extern crate env_logger;
extern crate hbbft;
extern crate pairing;
extern crate rand;
use std::collections::BTreeMap;
use hbbft::crypto::{PublicKey, SecretKey};
use hbbft::sync_key_gen::SyncKeyGen;
fn test_sync_key_gen_with(threshold: usize, node_num: usize) {
let mut rng = rand::thread_rng();
// Generate individual key pairs for encryption. These are not suitable for threshold schemes.
let sec_keys: Vec<SecretKey> = (0..node_num).map(|_| SecretKey::new(&mut rng)).collect();
let pub_keys: Vec<PublicKey> = sec_keys.iter().map(|sk| sk.public_key()).collect();
// Create the `SyncKeyGen` instances and initial proposals.
let mut nodes = Vec::new();
let proposals: Vec<_> = sec_keys
.into_iter()
.enumerate()
.map(|(idx, sk)| {
let (sync_key_gen, proposal) =
SyncKeyGen::new(idx as u64, sk, pub_keys.clone(), threshold);
nodes.push(sync_key_gen);
proposal
})
.collect();
// Handle the first `threshold + 1` proposals. Those should suffice for key generation.
let mut accepts = Vec::new();
for (sender_idx, proposal) in proposals[..=threshold].iter().enumerate() {
for (node_idx, node) in nodes.iter_mut().enumerate() {
let accept = node
.handle_propose(sender_idx as u64, proposal.clone())
.expect("valid proposal");
// Only the first `threshold + 1` manage to commit their `Accept`s.
if node_idx <= 2 * threshold {
accepts.push((node_idx, accept));
}
}
}
// Handle the `Accept`s from `2 * threshold + 1` nodes.
for (sender_idx, accept) in accepts {
for node in &mut nodes {
assert!(!node.is_ready()); // Not enough `Accept`s yet.
node.handle_accept(sender_idx as u64, accept.clone());
}
}
// Compute the keys and test a threshold signature.
let msg = "Help I'm trapped in a unit test factory";
let pub_key_set = nodes[0].generate().0;
let sig_shares: BTreeMap<_, _> = nodes
.iter()
.enumerate()
.map(|(idx, node)| {
assert!(node.is_ready());
let (pks, sk) = node.generate();
assert_eq!(pks, pub_key_set);
let sig = sk.sign(msg);
assert!(pks.public_key_share(idx as u64).verify(&sig, msg));
(idx as u64, sig)
})
.collect();
let sig = pub_key_set
.combine_signatures(sig_shares.iter().take(threshold + 1))
.expect("signature shares match");
assert!(pub_key_set.public_key().verify(&sig, msg));
}
#[test]
fn test_sync_key_gen() {
// This returns an error in all but the first test.
let _ = env_logger::try_init();
for &node_num in &[1, 2, 3, 4, 8, 15] {
let threshold = (node_num - 1) / 3;
test_sync_key_gen_with(threshold, node_num);
}
}