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frost-client: fix DKG with 2 participants
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@conradoplg
conradoplg committed Feb 25, 2025
1 parent 0cfe769 commit b3c62d5
Showing 1 changed file with 85 additions and 58 deletions.
143 changes: 85 additions & 58 deletions dkg/src/comms/http.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -133,10 +133,21 @@ impl<C: Ciphersuite> SessionState<C> {

// If complete, advance to next state
if round1_packages.len() == pubkeys.len() - 1 {
*self = SessionState::WaitingForRound1PackagesBroadcast {
pubkeys: pubkeys.clone(),
round1_packages: round1_packages.clone(),
round1_broadcasted_packages: Default::default(),
if pubkeys.len() > 2 {
*self = SessionState::WaitingForRound1PackagesBroadcast {
pubkeys: pubkeys.clone(),
round1_packages: round1_packages.clone(),
round1_broadcasted_packages: Default::default(),
}
} else {
// if pubkeys.len() == 2 then the echo broadcast protocol
// degenerates into a simple broadcast, so we can just skip
// the echo broadcast round.
*self = SessionState::WaitingForRound2Packages {
pubkeys: pubkeys.clone(),
round1_packages: round1_packages.clone(),
round2_packages: Default::default(),
}
}
}
Ok(())
Expand Down Expand Up @@ -265,7 +276,11 @@ impl<C: Ciphersuite> SessionState<C> {
/// When this returns `true`, [`round1_packages()`] can be called, but
/// its contents have not been checked via echo broadcast.
pub fn has_round1_packages(&self) -> bool {
matches!(self, SessionState::WaitingForRound1PackagesBroadcast { .. })
matches!(
self,
SessionState::WaitingForRound1PackagesBroadcast { .. }
| SessionState::WaitingForRound2Packages { .. }
)
}

/// Returns a map linking a participant identifier and the Round 1 Package
Expand All @@ -285,9 +300,11 @@ impl<C: Ciphersuite> SessionState<C> {
}
}

/// Returns if all participants sent their broadcast Round 1 Packages.
/// Returns if all participants sent their broadcast Round 1 Packages,
/// or if the echo broadcast round should be skipped.
///
/// When this returns `true`, [`round1_packages()`] can be called,
/// and its contents are ensure to be checked via echo broadcast.
/// and its contents are ensured to be checked via echo broadcast.
pub fn has_round1_broadcast_packages(&self) -> bool {
matches!(self, SessionState::WaitingForRound2Packages { .. })
}
Expand Down Expand Up @@ -542,6 +559,11 @@ impl<C: Ciphersuite + 'static> Comms<C> for HTTPComms<C> {
))
})
.collect::<Result<_, frost_core::Error<C>>>()?;

if self.pubkeys.len() < 2 {
return Err(eyre!("DKG session must have at least 2 participants").into());
}

// Copy the pubkeys into the state.
match self.state {
SessionState::WaitingForRound1Packages {
Expand Down Expand Up @@ -659,65 +681,70 @@ impl<C: Ciphersuite + 'static> Comms<C> for HTTPComms<C> {
}
eprintln!();

// Broadcast received Round 1 Packages to all other participants
for (recipient_pubkey, recipient_identifier) in self.pubkeys.clone().iter() {
// No need to broadcast to oneself
if Some(recipient_pubkey) == self.args.comm_pubkey.as_ref() {
continue;
}
for (sender_identifier, package) in self.state.round1_packages()?.iter() {
// No need to broadcast back to the sender
if *sender_identifier == *recipient_identifier {
// We might need to skip the echo broadcast if its not needed (e.g.
// only 2 participants)
if !self.state.has_round1_broadcast_packages() {
// Broadcast received Round 1 Packages to all other participants
for (recipient_pubkey, recipient_identifier) in self.pubkeys.clone().iter() {
// No need to broadcast to oneself
if Some(recipient_pubkey) == self.args.comm_pubkey.as_ref() {
continue;
}
let msg = self.encrypt(
recipient_pubkey,
serde_json::to_vec(&(*sender_identifier, package))?,
)?;
self.client
.post(format!("{}/send", self.host_port))
.bearer_auth(self.access_token.as_ref().expect("was just set"))
.json(&frostd::SendArgs {
session_id: self.session_id.expect("set before"),
recipients: vec![PublicKey(recipient_pubkey.clone())],
msg,
for (sender_identifier, package) in self.state.round1_packages()?.iter() {
// No need to broadcast back to the sender
if *sender_identifier == *recipient_identifier {
continue;
}
let msg = self.encrypt(
recipient_pubkey,
serde_json::to_vec(&(*sender_identifier, package))?,
)?;
self.client
.post(format!("{}/send", self.host_port))
.bearer_auth(self.access_token.as_ref().expect("was just set"))
.json(&frostd::SendArgs {
session_id: self.session_id.expect("set before"),
recipients: vec![PublicKey(recipient_pubkey.clone())],
msg,
})
.send()
.await?;
}
}

eprint!("Waiting for other participants to send their broadcasted Round 1 Packages...");

loop {
let r = self
.client
.post(format!("{}/receive", self.host_port))
.bearer_auth(
self.access_token
.as_ref()
.expect("must have been set before"),
)
.json(&frostd::ReceiveArgs {
session_id: self.session_id.unwrap(),
as_coordinator: false,
})
.send()
.await?
.json::<frostd::ReceiveOutput>()
.await?;
for msg in r.msgs {
let msg = self.decrypt(msg)?;
self.state
.recv(msg, self.identifier.expect("must have been set"))?;
}
tokio::time::sleep(Duration::from_secs(2)).await;
eprint!(".");
if self.state.has_round1_broadcast_packages() {
break;
}
}
eprintln!();
}

eprint!("Waiting for other participants to send their broadcasted Round 1 Packages...");

loop {
let r = self
.client
.post(format!("{}/receive", self.host_port))
.bearer_auth(
self.access_token
.as_ref()
.expect("must have been set before"),
)
.json(&frostd::ReceiveArgs {
session_id: self.session_id.unwrap(),
as_coordinator: false,
})
.send()
.await?
.json::<frostd::ReceiveOutput>()
.await?;
for msg in r.msgs {
let msg = self.decrypt(msg)?;
self.state
.recv(msg, self.identifier.expect("must have been set"))?;
}
tokio::time::sleep(Duration::from_secs(2)).await;
eprint!(".");
if self.state.has_round1_broadcast_packages() {
break;
}
}
eprintln!();
self.state.round1_packages()
}

Expand Down

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