add constructor, happy test for signing input #481

src/sign/interactive_sign/participant.rs

@@ -6,12 +6,13 @@
 // of this source tree.
 
 use rand::{CryptoRng, RngCore};
-use sha2::Sha256;
+use sha2::{Digest, Sha256};
 use tracing::{error, info};
 
 use crate::{
+    auxinfo,
     errors::{CallerError, InternalError, Result},
-    keygen::KeySharePublic,
+    keygen::{self, KeySharePublic},
     message_queue::MessageQueue,
     messages::{Message, MessageType, SignMessageType},
     participant::{ProcessOutcome, Status},
@@ -145,6 +146,33 @@ pub struct Input {
     presign_input: presign::Input,
 }
 
+impl Input {
+    /// Construct a new input for interactive signing from the outputs of the
+    /// [`auxinfo`](crate::auxinfo::AuxInfoParticipant) and
+    /// [`keygen`](crate::keygen::KeygenParticipant) protocols.
+    ///
+    /// The two output sets must have been generated by the same set of
+    /// participants (with the same set of [`ParticipantIdentifier`]s) and
+    /// private component of each output must correspond with the same
+    /// participant.
+    ///
+    /// The message should be the raw bytes of the message to be signed; do not
+    /// "pre-hash" the message. It is hashed here using SHA2-256.
+    pub fn new(
+        message: &[u8],
+        keygen_output: keygen::Output,
+        auxinfo_output: auxinfo::Output,
+    ) -> Result<Self> {
+        let presign_input = presign::Input::new(auxinfo_output, keygen_output)?;
+        let message_digest = Sha256::new().chain_update(message);
+
+        Ok(Self {
+            message_digest,
+            presign_input,
+        })
+    }
+}
+
 impl ProtocolParticipant for InteractiveSignParticipant {
     type Input = Input;
     type Output = Signature;
@@ -323,14 +351,25 @@ mod tests {
         keygen,
         messages::{Message, MessageType},
         participant::ProcessOutcome,
-        presign,
         sign::Signature,
         utils::testing::init_testing,
-        Identifier, ParticipantConfig, ProtocolParticipant,
+        Identifier, ParticipantConfig, ParticipantIdentifier, ProtocolParticipant,
     };
 
     use super::{Input, InteractiveSignParticipant, Status};
 
+    #[test]
+    fn input_from_valid_sources_is_valid() {
+        let rng = &mut init_testing();
+        let pids = std::iter::repeat_with(|| ParticipantIdentifier::random(rng))
+            .take(5)
+            .collect::<Vec<_>>();
+        let keygen_output = keygen::Output::simulate(&pids, rng);
+        let auxinfo_output = auxinfo::Output::simulate(&pids, rng);
+        let message = b"greetings from the new world";
+        assert!(Input::new(message, keygen_output, auxinfo_output).is_ok())
+    }
+
     /// Pick a random incoming message and have the correct participant process
     /// it.
     fn process_messages<'a>(
@@ -371,17 +410,13 @@ mod tests {
         let auxinfo_outputs = auxinfo::Output::simulate_set(&configs, rng);
 
         let message = b"in an old house in paris all covered in vines lived 12 little girls";
-        let message_digest = sha2::Sha256::new().chain_update(message);
 
         // Save the public key for later
         let public_key = &keygen_outputs[0].public_key().unwrap();
 
         let inputs = std::iter::zip(keygen_outputs, auxinfo_outputs)
             .map(|(keygen_output, auxinfo_output)| {
-                Ok(Input {
-                    message_digest: message_digest.clone(),
-                    presign_input: presign::Input::new(auxinfo_output, keygen_output)?,
-                })
+                Input::new(message, keygen_output, auxinfo_output)
             })
             .collect::<Result<Vec<_>>>()?;