Sign and send empty messages if a round doesn't send a specific messa…

…ge part
entropyxyz · Oct 25, 2024 · 0c8843b · 0c8843b
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Showing 15 changed files with 353 additions and 211 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,18 +13,23 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added a `Test` prefix to `testing::Signer`/`Verifier`/`Signature`/`Hasher` and renamed `TestingSessionParams` to `TestSessionParams`. ([#40])
 - `SessionId::new()` renamed to `from_seed()`. ([#41])
 - `FirstRound::new()` takes a `&[u8]` instead of a `SessionId` object. ([#41])
+- The signatures of `Round::make_echo_broadcast()`, `Round::make_direct_message()`, and `Round::receive_message()`, take messages without `Option`s. ([#46])
+- `Round::make_direct_message_with_artifact()` is the method returning an artifact now; `Round::make_direct_message()` is a shortcut for cases where no artifact is returned. ([#46])
+- `Artifact::empty()` removed, the user should return `None` instead. ([#46])
 
 
 ### Added
 
 - `SerializableMap` wrapper for `BTreeMap` supporting more formats and providing some safety features. (#[32])
+- `DirectMessage::assert_is_none()` and `verify_is_some()`, same for `EchoBroadcast`. Users can now check that a part of the round message (echo or direct) is `None` as expected, and make a verifiable evidence if it is not. ([#46])
 
 
 [#32]: https://github.com/entropyxyz/manul/pull/32
 [#36]: https://github.com/entropyxyz/manul/pull/36
 [#37]: https://github.com/entropyxyz/manul/pull/37
 [#40]: https://github.com/entropyxyz/manul/pull/40
 [#41]: https://github.com/entropyxyz/manul/pull/41
+[#46]: https://github.com/entropyxyz/manul/pull/46
 
 
 ## [0.0.1] - 2024-10-12

diff --git a/examples/src/simple.rs b/examples/src/simple.rs
@@ -36,7 +36,7 @@ impl ProtocolError for SimpleProtocolError {
 
     fn verify_messages_constitute_error(
         &self,
-        _echo_broadcast: &Option<EchoBroadcast>,
+        _echo_broadcast: &EchoBroadcast,
         direct_message: &DirectMessage,
         _echo_broadcasts: &BTreeMap<RoundId, EchoBroadcast>,
         _direct_messages: &BTreeMap<RoundId, DirectMessage>,
@@ -87,10 +87,22 @@ impl Protocol for SimpleProtocol {
         round_id: RoundId,
         message: &DirectMessage,
     ) -> Result<(), MessageValidationError> {
-        if round_id == RoundId::new(1) {
-            return message.verify_is_invalid::<Self, Round1Message>();
+        match round_id {
+            r if r == RoundId::new(1) => message.verify_is_not::<Self, Round1Message>(),
+            r if r == RoundId::new(2) => message.verify_is_not::<Self, Round2Message>(),
+            _ => Err(MessageValidationError::InvalidEvidence("Invalid round number".into())),
+        }
+    }
+
+    fn verify_echo_broadcast_is_invalid(
+        round_id: RoundId,
+        message: &EchoBroadcast,
+    ) -> Result<(), MessageValidationError> {
+        match round_id {
+            r if r == RoundId::new(1) => message.verify_is_some(),
+            r if r == RoundId::new(2) => message.verify_is_not::<Self, Round2Message>(),
+            _ => Err(MessageValidationError::InvalidEvidence("Invalid round number".into())),
         }
-        Err(MessageValidationError::InvalidEvidence("Invalid round number".into()))?
     }
 }
 
@@ -171,41 +183,41 @@ impl<Id: 'static + Debug + Clone + Ord + Send + Sync> Round<Id> for Round1<Id> {
         &self.context.other_ids
     }
 
-    fn make_echo_broadcast(&self, _rng: &mut impl CryptoRngCore) -> Option<Result<EchoBroadcast, LocalError>> {
+    fn make_echo_broadcast(&self, _rng: &mut impl CryptoRngCore) -> Result<EchoBroadcast, LocalError> {
         debug!("{:?}: making echo broadcast", self.context.id);
 
         let message = Round1Echo {
             my_position: self.context.ids_to_positions[&self.context.id],
         };
 
-        Some(Self::serialize_echo_broadcast(message))
+        Self::serialize_echo_broadcast(message)
     }
 
     fn make_direct_message(
         &self,
         _rng: &mut impl CryptoRngCore,
         destination: &Id,
-    ) -> Result<(DirectMessage, Artifact), LocalError> {
+    ) -> Result<DirectMessage, LocalError> {
         debug!("{:?}: making direct message for {:?}", self.context.id, destination);
 
         let message = Round1Message {
             my_position: self.context.ids_to_positions[&self.context.id],
             your_position: self.context.ids_to_positions[destination],
         };
         let dm = Self::serialize_direct_message(message)?;
-        let artifact = Artifact::empty();
-        Ok((dm, artifact))
+        Ok(dm)
     }
 
     fn receive_message(
         &self,
         _rng: &mut impl CryptoRngCore,
         from: &Id,
-        _echo_broadcast: Option<EchoBroadcast>,
+        echo_broadcast: EchoBroadcast,
         direct_message: DirectMessage,
     ) -> Result<Payload, ReceiveError<Id, Self::Protocol>> {
         debug!("{:?}: receiving message from {:?}", self.context.id, from);
 
+        let _echo = echo_broadcast.deserialize::<SimpleProtocol, Round1Echo>()?;
         let message = direct_message.deserialize::<SimpleProtocol, Round1Message>()?;
 
         debug!("{:?}: received message: {:?}", self.context.id, message);
@@ -275,41 +287,34 @@ impl<Id: 'static + Debug + Clone + Ord + Send + Sync> Round<Id> for Round2<Id> {
         &self.context.other_ids
     }
 
-    fn make_echo_broadcast(&self, _rng: &mut impl CryptoRngCore) -> Option<Result<EchoBroadcast, LocalError>> {
-        debug!("{:?}: making echo broadcast", self.context.id);
-
-        let message = Round1Echo {
-            my_position: self.context.ids_to_positions[&self.context.id],
-        };
-
-        Some(Self::serialize_echo_broadcast(message))
-    }
+    // Does not send echo broadcasts
 
     fn make_direct_message(
         &self,
         _rng: &mut impl CryptoRngCore,
         destination: &Id,
-    ) -> Result<(DirectMessage, Artifact), LocalError> {
+    ) -> Result<DirectMessage, LocalError> {
         debug!("{:?}: making direct message for {:?}", self.context.id, destination);
 
         let message = Round1Message {
             my_position: self.context.ids_to_positions[&self.context.id],
             your_position: self.context.ids_to_positions[destination],
         };
         let dm = Self::serialize_direct_message(message)?;
-        let artifact = Artifact::empty();
-        Ok((dm, artifact))
+        Ok(dm)
     }
 
     fn receive_message(
         &self,
         _rng: &mut impl CryptoRngCore,
         from: &Id,
-        _echo_broadcast: Option<EchoBroadcast>,
+        echo_broadcast: EchoBroadcast,
         direct_message: DirectMessage,
     ) -> Result<Payload, ReceiveError<Id, Self::Protocol>> {
         debug!("{:?}: receiving message from {:?}", self.context.id, from);
 
+        echo_broadcast.assert_is_none()?;
+
         let message = direct_message.deserialize::<SimpleProtocol, Round1Message>()?;
 
         debug!("{:?}: received message: {:?}", self.context.id, message);

diff --git a/examples/src/simple_malicious.rs b/examples/src/simple_malicious.rs
@@ -57,21 +57,17 @@ impl<Id: 'static + Debug + Clone + Ord + Send + Sync> FirstRound<Id> for Malicio
 }
 
 impl<Id: 'static + Debug + Clone + Ord + Send + Sync> RoundOverride<Id> for MaliciousRound1<Id> {
-    fn make_direct_message(
-        &self,
-        rng: &mut impl CryptoRngCore,
-        destination: &Id,
-    ) -> Result<(DirectMessage, Artifact), LocalError> {
+    fn make_direct_message(&self, rng: &mut impl CryptoRngCore, destination: &Id) -> Result<DirectMessage, LocalError> {
         if matches!(self.behavior, Behavior::SerializedGarbage) {
             let dm = DirectMessage::new::<<Self::InnerRound as Round<Id>>::Protocol, _>(&[99u8]).unwrap();
-            Ok((dm, Artifact::empty()))
+            Ok(dm)
         } else if matches!(self.behavior, Behavior::AttributableFailure) {
             let message = Round1Message {
                 my_position: self.round.context.ids_to_positions[&self.round.context.id],
                 your_position: self.round.context.ids_to_positions[&self.round.context.id],
             };
             let dm = DirectMessage::new::<<Self::InnerRound as Round<Id>>::Protocol, _>(&message)?;
-            Ok((dm, Artifact::empty()))
+            Ok(dm)
         } else {
             self.inner_round_ref().make_direct_message(rng, destination)
         }
@@ -121,18 +117,14 @@ impl<Id: 'static + Debug + Clone + Ord + Send + Sync> RoundWrapper<Id> for Malic
 }
 
 impl<Id: 'static + Debug + Clone + Ord + Send + Sync> RoundOverride<Id> for MaliciousRound2<Id> {
-    fn make_direct_message(
-        &self,
-        rng: &mut impl CryptoRngCore,
-        destination: &Id,
-    ) -> Result<(DirectMessage, Artifact), LocalError> {
+    fn make_direct_message(&self, rng: &mut impl CryptoRngCore, destination: &Id) -> Result<DirectMessage, LocalError> {
         if matches!(self.behavior, Behavior::AttributableFailureRound2) {
             let message = Round2Message {
                 my_position: self.round.context.ids_to_positions[&self.round.context.id],
                 your_position: self.round.context.ids_to_positions[&self.round.context.id],
             };
             let dm = DirectMessage::new::<<Self::InnerRound as Round<Id>>::Protocol, _>(&message)?;
-            Ok((dm, Artifact::empty()))
+            Ok(dm)
         } else {
             self.inner_round_ref().make_direct_message(rng, destination)
         }

diff --git a/manul/benches/empty_rounds.rs b/manul/benches/empty_rounds.rs
@@ -24,7 +24,7 @@ pub struct EmptyProtocolError;
 impl ProtocolError for EmptyProtocolError {
     fn verify_messages_constitute_error(
         &self,
-        _echo_broadcast: &Option<EchoBroadcast>,
+        _echo_broadcast: &EchoBroadcast,
         _direct_message: &DirectMessage,
         _echo_broadcasts: &BTreeMap<RoundId, EchoBroadcast>,
         _direct_messages: &BTreeMap<RoundId, DirectMessage>,
@@ -108,34 +108,36 @@ impl<Id: 'static + Debug + Clone + Ord + Send + Sync> Round<Id> for EmptyRound<I
         &self.inputs.other_ids
     }
 
-    fn make_echo_broadcast(&self, _rng: &mut impl CryptoRngCore) -> Option<Result<EchoBroadcast, LocalError>> {
+    fn make_echo_broadcast(&self, _rng: &mut impl CryptoRngCore) -> Result<EchoBroadcast, LocalError> {
         if self.inputs.echo {
-            Some(Self::serialize_echo_broadcast(Round1EchoBroadcast))
+            Self::serialize_echo_broadcast(Round1EchoBroadcast)
         } else {
-            None
+            Ok(EchoBroadcast::none())
         }
     }
 
-    fn make_direct_message(
+    fn make_direct_message_with_artifact(
         &self,
         _rng: &mut impl CryptoRngCore,
         _destination: &Id,
-    ) -> Result<(DirectMessage, Artifact), LocalError> {
+    ) -> Result<(DirectMessage, Option<Artifact>), LocalError> {
         let dm = Self::serialize_direct_message(Round1DirectMessage)?;
         let artifact = Artifact::new(Round1Artifact);
-        Ok((dm, artifact))
+        Ok((dm, Some(artifact)))
     }
 
     fn receive_message(
         &self,
         _rng: &mut impl CryptoRngCore,
         _from: &Id,
-        echo_broadcast: Option<EchoBroadcast>,
+        echo_broadcast: EchoBroadcast,
         direct_message: DirectMessage,
     ) -> Result<Payload, ReceiveError<Id, Self::Protocol>> {
-        let _echo_broadcast = echo_broadcast
-            .map(|echo| echo.deserialize::<EmptyProtocol, Round1EchoBroadcast>())
-            .transpose()?;
+        if self.inputs.echo {
+            let _echo_broadcast = echo_broadcast.deserialize::<EmptyProtocol, Round1EchoBroadcast>()?;
+        } else {
+            echo_broadcast.assert_is_none()?;
+        }
         let _direct_message = direct_message.deserialize::<EmptyProtocol, Round1DirectMessage>()?;
         Ok(Payload::new(Round1Payload))
     }

diff --git a/manul/src/protocol.rs b/manul/src/protocol.rs
@@ -12,16 +12,17 @@ For more details, see the documentation of the mentioned traits.
 */
 
 mod errors;
+mod message;
 mod object_safe;
 mod round;
 
 pub use errors::{
     DeserializationError, DirectMessageError, EchoBroadcastError, FinalizeError, LocalError, MessageValidationError,
     ProtocolValidationError, ReceiveError, RemoteError,
 };
+pub use message::{DirectMessage, EchoBroadcast};
 pub use round::{
-    AnotherRound, Artifact, DirectMessage, EchoBroadcast, FinalizeOutcome, FirstRound, Payload, Protocol,
-    ProtocolError, Round, RoundId,
+    AnotherRound, Artifact, FinalizeOutcome, FirstRound, Payload, Protocol, ProtocolError, Round, RoundId,
 };
 
 pub(crate) use errors::ReceiveErrorType;

diff --git a/manul/src/protocol/errors.rs b/manul/src/protocol/errors.rs
@@ -193,7 +193,13 @@ impl From<LocalError> for ProtocolValidationError {
 pub struct DirectMessageError(DeserializationError);
 
 impl DirectMessageError {
-    pub(crate) fn new(error: DeserializationError) -> Self {
+    pub(crate) fn new(message: impl Into<String>) -> Self {
+        Self(DeserializationError::new(message))
+    }
+}
+
+impl From<DeserializationError> for DirectMessageError {
+    fn from(error: DeserializationError) -> Self {
         Self(error)
     }
 }
@@ -204,7 +210,13 @@ impl DirectMessageError {
 pub struct EchoBroadcastError(DeserializationError);
 
 impl EchoBroadcastError {
-    pub(crate) fn new(error: DeserializationError) -> Self {
+    pub(crate) fn new(message: impl Into<String>) -> Self {
+        Self(DeserializationError::new(message))
+    }
+}
+
+impl From<DeserializationError> for EchoBroadcastError {
+    fn from(error: DeserializationError) -> Self {
         Self(error)
     }
 }