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Refactor messages, distinguish broadcast and unicast #3

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merged 8 commits into from
Sep 9, 2024
Merged

Refactor messages, distinguish broadcast and unicast #3

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0fbd004
feat: distinguish broadcast and unicast messages
MarekMracna Jul 29, 2024
c7e64fa
chore: bump version to 0.3.0
MarekMracna Jul 29, 2024
9d4d0ee
refactor: sensible error handling
MarekMracna Aug 17, 2024
6f84a6c
feat: hashmaps in protocol messages
MarekMracna Aug 26, 2024
4ba2f79
refactor: follow rustfmt
MarekMracna Aug 26, 2024
20ab5f1
test: replace indices vector with hashmap
MarekMracna Aug 26, 2024
404cf6a
refactor: more flexible iterator usage
MarekMracna Sep 4, 2024
8e3e61d
docs: reword and annotate a few doccomments
MarekMracna Sep 4, 2024
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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
[package]
name = "meesign-crypto"
version = "0.2.0"
version = "0.3.0"
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
Expand Down
11 changes: 9 additions & 2 deletions proto/meesign.proto
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,14 @@ message ProtocolInit {
bytes data = 4;
}

message ProtocolMessage {
message ClientMessage {
ProtocolType protocol_type = 1;
repeated bytes message = 2;
map<uint32, bytes> unicasts = 2;
optional bytes broadcast = 3;
}

message ServerMessage {
ProtocolType protocol_type = 1;
map<uint32, bytes> unicasts = 2;
map<uint32, bytes> broadcasts = 3;
}
134 changes: 57 additions & 77 deletions src/protocol/elgamal.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use crate::proto::{ProtocolGroupInit, ProtocolInit, ProtocolType};
use crate::proto::{ProtocolGroupInit, ProtocolInit, ProtocolType, ServerMessage};
use crate::protocol::*;
use curve25519_dalek::{
ristretto::{CompressedRistretto, RistrettoPoint},
Expand All @@ -19,6 +19,8 @@ use aes_gcm::{
use prost::Message;
use serde::{Deserialize, Serialize};

use std::collections::HashMap;

#[derive(Serialize, Deserialize)]
pub(crate) struct KeygenContext {
round: KeygenRound,
Expand All @@ -27,9 +29,9 @@ pub(crate) struct KeygenContext {
#[derive(Serialize, Deserialize)]
enum KeygenRound {
R0,
R1(ParticipantCollectingCommitments<Ristretto>, u16),
R2(ParticipantCollectingPolynomials<Ristretto>, u16),
R3(ParticipantExchangingSecrets<Ristretto>, u16),
R1(ParticipantCollectingCommitments<Ristretto>),
R2(ParticipantCollectingPolynomials<Ristretto>),
R3(ParticipantExchangingSecrets<Ristretto>),
Done(ActiveParticipant<Ristretto>),
}

Expand All @@ -49,83 +51,73 @@ impl KeygenContext {
let dkg =
ParticipantCollectingCommitments::<Ristretto>::new(params, index.into(), &mut OsRng);
let c = dkg.commitment();
let ser = serialize_bcast(&c, msg.parties as usize - 1)?;
self.round = KeygenRound::R1(dkg, index);
Ok(pack(ser, ProtocolType::Elgamal))
let msg = serialize_bcast(&c, ProtocolType::Elgamal)?;
self.round = KeygenRound::R1(dkg);
Ok(msg)
}

fn update(&mut self, data: &[u8]) -> Result<Vec<u8>> {
let msgs = unpack(data)?;
let n = msgs.len();
let msgs = ServerMessage::decode(data)?;

let (c, ser) = match &self.round {
let (c, msg) = match &self.round {
KeygenRound::R0 => return Err("protocol not initialized".into()),
KeygenRound::R1(dkg, idx) => {
KeygenRound::R1(dkg) => {
let mut dkg = dkg.clone();
let data = deserialize_vec(&msgs)?;
for (mut i, msg) in data.into_iter().enumerate() {
if i >= *idx as usize {
i += 1;
}
dkg.insert_commitment(i, msg);
let data = deserialize_map(&msgs.broadcasts)?;
for (i, msg) in data {
dkg.insert_commitment(i as usize, msg);
}
if dkg.missing_commitments().next().is_some() {
return Err("not enough commitments".into());
}
let dkg = dkg.finish_commitment_phase();
let public_info = dkg.public_info();
let ser = serialize_bcast(&public_info, n)?;
let msg = serialize_bcast(&public_info, ProtocolType::Elgamal)?;

(KeygenRound::R2(dkg, *idx), ser)
(KeygenRound::R2(dkg), msg)
}
KeygenRound::R2(dkg, idx) => {
KeygenRound::R2(dkg) => {
let mut dkg = dkg.clone();
let data = deserialize_vec(&msgs)?;
for (mut i, msg) in data.into_iter().enumerate() {
if i >= *idx as usize {
i += 1;
}
dkg.insert_public_polynomial(i, msg)?
let data = deserialize_map(&msgs.broadcasts)?;
for (i, msg) in data {
dkg.insert_public_polynomial(i as usize, msg)?
}
if dkg.missing_public_polynomials().next().is_some() {
return Err("not enough polynomials".into());
}
let dkg = dkg.finish_polynomials_phase();

let mut shares = Vec::new();
for mut i in 0..n {
if i >= *idx as usize {
i += 1;
}
let secret_share = dkg.secret_share_for_participant(i);
shares.push(secret_share);
}
let ser = serialize_uni(shares)?;
let shares = msgs
.broadcasts
.into_keys()
.map(|i| (i, dkg.secret_share_for_participant(i as usize)));

let msg = serialize_uni(shares, ProtocolType::Elgamal)?;

(KeygenRound::R3(dkg, *idx), ser)
(KeygenRound::R3(dkg), msg)
}
KeygenRound::R3(dkg, idx) => {
KeygenRound::R3(dkg) => {
let mut dkg = dkg.clone();
let data = deserialize_vec(&msgs)?;
for (mut i, msg) in data.into_iter().enumerate() {
if i >= *idx as usize {
i += 1;
}
dkg.insert_secret_share(i, msg)?;
let data = deserialize_map(&msgs.unicasts)?;
for (i, msg) in data {
dkg.insert_secret_share(i as usize, msg)?;
}
if dkg.missing_shares().next().is_some() {
return Err("not enough shares".into());
}
let dkg = dkg.complete()?;
let ser = inflate(dkg.key_set().shared_key().as_bytes().to_vec(), n);

(KeygenRound::Done(dkg), ser)
let msg = encode_raw_bcast(
dkg.key_set().shared_key().as_bytes().to_vec(),
ProtocolType::Elgamal,
);
(KeygenRound::Done(dkg), msg)
}
KeygenRound::Done(_) => return Err("protocol already finished".into()),
};

self.round = c;
Ok(pack(ser, ProtocolType::Elgamal))
Ok(msg)
}
}

Expand Down Expand Up @@ -160,7 +152,6 @@ pub(crate) struct DecryptContext {
ctx: ActiveParticipant<Ristretto>,
encrypted_key: Ciphertext<Ristretto>,
data: (Vec<u8>, Vec<u8>, Vec<u8>),
indices: Vec<u16>,
shares: Vec<(usize, VerifiableDecryption<Ristretto>)>,
result: Option<Vec<u8>>,
}
Expand All @@ -173,21 +164,20 @@ impl DecryptContext {
return Err("wrong protocol type".into());
}

self.indices = msg.indices.clone().into_iter().map(|i| i as u16).collect();
self.data = serde_json::from_slice(&msg.data)?;
self.encrypted_key = serde_json::from_slice(&self.data.0)?;

let (share, proof) = self.ctx.decrypt_share(self.encrypted_key, &mut OsRng);

let ser = serialize_bcast(
let msg = serialize_bcast(
&serde_json::to_string(&(share, proof))?.as_bytes(),
self.indices.len() - 1,
ProtocolType::Elgamal,
)?;

let share = (self.ctx.index(), share);
self.shares.push(share);

Ok(pack(ser, ProtocolType::Elgamal))
Ok(msg)
}

fn update(&mut self, data: &[u8]) -> Result<Vec<u8>> {
Expand All @@ -198,32 +188,17 @@ impl DecryptContext {
return Err("protocol already finished".into());
}

let msgs = unpack(data)?;
let msgs = ServerMessage::decode(data)?;

let data: Vec<Vec<u8>> = deserialize_vec(&msgs)?;
let local_index = self
.indices
.iter()
.position(|x| *x as usize == self.ctx.index())
.ok_or("participant index not included")?;
assert_eq!(self.ctx.index(), self.indices[local_index] as usize);

for (mut i, msg) in data.into_iter().enumerate() {
if i >= local_index {
i += 1;
}
let data: HashMap<u32, Vec<u8>> = deserialize_map(&msgs.broadcasts)?;
for (i, msg) in data {
let msg: (VerifiableDecryption<Ristretto>, LogEqualityProof<Ristretto>) =
serde_json::from_slice(&msg)?;
self.ctx
.key_set()
.verify_share(
msg.0.into(),
self.encrypted_key,
self.indices[i].into(),
&msg.1,
)
.verify_share(msg.0.into(), self.encrypted_key, i as usize, &msg.1)
.unwrap();
self.shares.push((self.indices[i].into(), msg.0));
self.shares.push((i as usize, msg.0));
}

let mut key = [0u8; 16];
Expand Down Expand Up @@ -254,8 +229,8 @@ impl DecryptContext {

self.result = Some(msg.clone());

let ser = inflate(msg, self.indices.len() - 1);
Ok(pack(ser, ProtocolType::Elgamal))
let msg = encode_raw_bcast(msg, ProtocolType::Elgamal);
Ok(msg)
}
}

Expand Down Expand Up @@ -284,7 +259,6 @@ impl ThresholdProtocol for DecryptContext {
ctx: serde_json::from_slice(group).expect("could not deserialize group context"),
encrypted_key: Ciphertext::zero(),
data: (Vec::new(), Vec::new(), Vec::new()),
indices: Vec::new(),
shares: Vec::new(),
result: None,
}
Expand Down Expand Up @@ -374,6 +348,8 @@ mod tests {
let (pks, _) =
<KeygenContext as KeygenProtocolTest>::run(threshold as u32, parties as u32);

let pks: Vec<_> = pks.into_values().collect();

for i in 1..parties {
assert_eq!(pks[0], pks[i])
}
Expand All @@ -387,13 +363,17 @@ mod tests {
for parties in threshold..6 {
let (pks, ctxs) =
<KeygenContext as KeygenProtocolTest>::run(threshold as u32, parties as u32);
let pks: Vec<_> = pks.into_values().collect();
let msg = b"hello";
let ct = encrypt(msg, &pks[0]).unwrap();

let mut indices = (0..parties as u16).choose_multiple(&mut OsRng, threshold);
indices.sort();
let ctxs = ctxs
.into_iter()
.choose_multiple(&mut OsRng, threshold)
.into_iter()
.collect();
let results =
<DecryptContext as ThresholdProtocolTest>::run(ctxs, indices, ct.to_vec());
<DecryptContext as ThresholdProtocolTest>::run(ctxs, ct.to_vec());

for result in results {
assert_eq!(&msg.to_vec(), &result);
Expand Down
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