Merge pull request #58 from earthstar-project/commitment-reveal-sending

WGPS: Commitment scheme

wgps/Cargo.toml

@@ -5,7 +5,9 @@ edition = "2021"
 
 [dependencies]
 willow-data-model = { path = "../data-model", version = "0.1.0" }
+willow-encoding = { path = "../encoding", version = "0.1.0" }
 ufotofu = { version = "0.4.2", features = ["std"] }
+futures = { version = "0.3.31" }
 either = "1.10.0"
 
 [dev-dependencies]

wgps/src/commitment_scheme/execute_prelude.rs

@@ -0,0 +1,80 @@
+use futures::future::{try_select, Either};
+
+// send our own commitment reveal message only after we have received the prelude.
+
+// everything that needs the challenge has to wait until we have received their commitment reveal message.
+
+use ufotofu::local_nb::{BulkConsumer, BulkProducer};
+use willow_encoding::Encodable;
+
+use crate::{ChallengeHash, CommitmentReveal};
+
+use super::{
+    receive_prelude::{receive_prelude, ReceivePreludeError, ReceivedPrelude},
+    send_prelude::send_prelude,
+};
+
+/// An error which only occurs during the initial phase of a WGPS session.
+pub enum ExecutePreludeError<E> {
+    /// There was a problem receiving their prelude.
+    ReceiveError(ReceivePreludeError<E>),
+    /// There was a problem sending our prelude.
+    SendError(E),
+}
+
+impl<E> From<ReceivePreludeError<E>> for ExecutePreludeError<E> {
+    fn from(value: ReceivePreludeError<E>) -> Self {
+        ExecutePreludeError::ReceiveError(value)
+    }
+}
+
+impl<E> From<E> for ExecutePreludeError<E> {
+    fn from(value: E) -> Self {
+        ExecutePreludeError::SendError(value)
+    }
+}
+
+impl<E: core::fmt::Display> core::fmt::Display for ExecutePreludeError<E> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ExecutePreludeError::ReceiveError(receive_prelude_error) => {
+                write!(f, "{}", receive_prelude_error)
+            }
+            ExecutePreludeError::SendError(error) => write!(f, "{}", error),
+        }
+    }
+}
+
+/// Given a consumer and producer, send a max payload size and commitment, and wait for the other side's corresponding `ReceivedPrelude`. Then send a `CommitmentReveal` message, before finally returning the received prelude.
+///
+/// Attention: waiting for the other peer's prelude means that we delay sending our first messages, even though technically we would be allowed to do that. PRs welcome.
+pub(crate) async fn execute_prelude<
+    const CHALLENGE_LENGTH: usize,
+    const CHALLENGE_HASH_LENGTH: usize,
+    CH: ChallengeHash<CHALLENGE_LENGTH, CHALLENGE_HASH_LENGTH>,
+    E,
+    C: BulkConsumer<Item = u8, Error = E>,
+    P: BulkProducer<Item = u8, Error = E>,
+>(
+    max_payload_power: u8,
+    our_nonce: [u8; CHALLENGE_LENGTH],
+    consumer: &mut C,
+    producer: &mut P,
+) -> Result<ReceivedPrelude<CHALLENGE_HASH_LENGTH>, ExecutePreludeError<E>> {
+    let commitment = CH::hash(our_nonce);
+
+    let receive_fut = Box::pin(receive_prelude::<CHALLENGE_HASH_LENGTH, _>(producer));
+    let send_fut = Box::pin(send_prelude(max_payload_power, commitment, consumer));
+
+    let (received_prelude, ()) = match try_select(receive_fut, send_fut).await {
+        Ok(Either::Left((received, send_fut))) => (received, send_fut.await?),
+        Ok(Either::Right(((), receive_fut))) => (receive_fut.await?, ()),
+        Err(Either::Left((error, _))) => return Err(error.into()),
+        Err(Either::Right((error, _))) => return Err(error.into()),
+    };
+
+    let msg = CommitmentReveal { nonce: our_nonce };
+    msg.encode(consumer).await?;
+
+    Ok(received_prelude)
+}

wgps/src/commitment_scheme/mod.rs

@@ -0,0 +1,3 @@
+pub mod execute_prelude;
+pub mod receive_prelude;
+pub mod send_prelude;