Add primitives to sign/verify arbitrary messages (GH-4655)

ironfish-rust/src/errors.rs

@@ -65,6 +65,7 @@ pub enum IronfishErrorKind {
     RandomnessError,
     RoundTwoSigningFailure,
     TryFromInt,
+    Unsupported,
     Utf8,
 }
 

ironfish-rust/src/lib.rs

@@ -17,6 +17,7 @@ pub mod rolling_filter;
 pub mod sapling_bls12;
 pub mod serializing;
 pub mod signal_catcher;
+pub mod signing;
 pub mod transaction;
 pub mod util;
 pub mod witness;

ironfish-rust/src/signing.rs

@@ -0,0 +1,222 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Methods to sign arbitrary message using Iron Fish keys. Note that this module cannot be used to
+//! sign or verify transactions.
+//!
+//! The signature scheme used is RedDSA on the JubJub curve (RedJubJub). Signatures are produced
+//! using the [Incoming View Key](crate::keys::IncomingViewKey) and verified using the [Public
+//! Address](crate::keys::PublicAddress).
+//!
+//! See [`ironfish_rust::transaction`] for methods to sign/verify transactions.
+//!
+//! # Examples
+//!
+//! ```
+//! use ironfish::keys::SaplingKey;
+//! use ironfish::signing::sign_message;
+//! use ironfish::signing::verify_message;
+//!
+//! // Generate keys for signing
+//! let secret_key = SaplingKey::generate_key();
+//!
+//! // Sign a message
+//! let message = b"some arbitrary message";
+//! let signature = sign_message(&secret_key, message, rand::thread_rng());
+//!
+//! // Get the keys for verification
+//! let public_address = secret_key.public_address();
+//!
+//! // Verify the signature
+//! match verify_message(&public_address, message, &signature) {
+//!     Ok(()) => println!("verification succeeded"),
+//!     Err(err) => println!("verification failed: {err}"),
+//! }
+//! ```
+
+use crate::{
+    errors::{IronfishError, IronfishErrorKind},
+    PublicAddress, SaplingKey,
+};
+use ironfish_zkp::{
+    constants::PUBLIC_KEY_GENERATOR,
+    redjubjub::{PrivateKey, PublicKey, Signature},
+};
+use rand::{CryptoRng, RngCore};
+use std::io;
+
+const VERSION: u8 = 0xa7u8;
+
+pub type MessageSignatureBytes = [u8; 65];
+
+#[derive(Copy, Clone, Debug)]
+pub struct MessageSignature(Signature);
+
+impl MessageSignature {
+    pub fn to_bytes(&self) -> MessageSignatureBytes {
+        let mut bytes = [0u8; 65];
+        self.write(&mut bytes[..])
+            .expect("serializing to an array of the correct size should never fail");
+        bytes
+    }
+
+    pub fn from_bytes(bytes: &MessageSignatureBytes) -> Self {
+        Self::read(&bytes[..])
+            .expect("deserializing an array of the correct size should never fail")
+    }
+
+    pub fn read<R: io::Read>(mut reader: R) -> Result<Self, IronfishError> {
+        let mut version = [0u8; 1];
+        reader.read_exact(&mut version)?;
+        if version != [VERSION] {
+            return Err(IronfishError::new(IronfishErrorKind::Unsupported));
+        }
+
+        let signature = Signature::read(reader)?;
+        Ok(signature.into())
+    }
+
+    pub fn write<W: io::Write>(&self, mut writer: W) -> Result<(), IronfishError> {
+        writer.write_all(&[VERSION])?;
+        self.0.write(writer)?;
+        Ok(())
+    }
+}
+
+impl AsRef<Signature> for MessageSignature {
+    #[inline]
+    fn as_ref(&self) -> &Signature {
+        &self.0
+    }
+}
+
+impl From<Signature> for MessageSignature {
+    #[inline]
+    fn from(signature: Signature) -> Self {
+        Self(signature)
+    }
+}
+
+impl From<MessageSignature> for Signature {
+    #[inline]
+    fn from(signature: MessageSignature) -> Self {
+        signature.0
+    }
+}
+
+impl From<MessageSignatureBytes> for MessageSignature {
+    #[inline]
+    fn from(bytes: MessageSignatureBytes) -> Self {
+        Self::from_bytes(&bytes)
+    }
+}
+
+impl From<MessageSignature> for MessageSignatureBytes {
+    #[inline]
+    fn from(signature: MessageSignature) -> Self {
+        signature.to_bytes()
+    }
+}
+
+fn signing_key(secret_key: &SaplingKey) -> PrivateKey {
+    PrivateKey(secret_key.incoming_viewing_key.view_key)
+}
+
+fn verification_key(public_address: &PublicAddress) -> PublicKey {
+    PublicKey(public_address.0.into())
+}
+
+/// Signs a message using the Incoming View Key.
+///
+/// The signature can be verified with [`verify_message()`] using the [Public
+/// Address](crate::keys::PublicAddress).
+pub fn sign_message<R: RngCore + CryptoRng>(
+    secret_key: &SaplingKey,
+    message: &[u8],
+    mut rng: R,
+) -> MessageSignature {
+    signing_key(secret_key)
+        .sign(message, &mut rng, *PUBLIC_KEY_GENERATOR)
+        .into()
+}
+
+/// Verifies a signature produced by [`sign_message()`].
+pub fn verify_message(
+    public_address: &PublicAddress,
+    message: &[u8],
+    signature: &MessageSignature,
+) -> Result<(), IronfishError> {
+    match verification_key(public_address).verify(message, &signature.0, *PUBLIC_KEY_GENERATOR) {
+        true => Ok(()),
+        false => Err(IronfishError::new(IronfishErrorKind::InvalidSignature)),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{
+        signing::{sign_message, verify_message, MessageSignature},
+        SaplingKey,
+    };
+    use rand::thread_rng;
+
+    #[test]
+    fn roundtrip() {
+        let secret_key = SaplingKey::generate_key();
+        let public_address = secret_key.public_address();
+        let message = b"test message";
+
+        let signature = sign_message(&secret_key, message, thread_rng());
+        verify_message(&public_address, message, &signature).expect("verification should pass");
+    }
+
+    #[test]
+    fn roundtrip_with_serialization() {
+        let secret_key = SaplingKey::generate_key();
+        let public_address = secret_key.public_address();
+        let message = b"test message";
+
+        let signature = sign_message(&secret_key, message, thread_rng());
+        let serialized_signature = signature.to_bytes();
+        let deserialized_signature = MessageSignature::from_bytes(&serialized_signature);
+        verify_message(&public_address, message, &deserialized_signature)
+            .expect("verification should pass");
+    }
+
+    #[test]
+    fn non_determinism() {
+        let secret_key = SaplingKey::generate_key();
+        let message = b"test message";
+
+        // Sign the same message twice with the same key, and verify that the output is different
+        // each time
+        let signature1 = sign_message(&secret_key, message, thread_rng());
+        let signature2 = sign_message(&secret_key, message, thread_rng());
+
+        assert_ne!(signature1.to_bytes(), signature2.to_bytes());
+    }
+
+    #[test]
+    fn verify_fails_with_wrong_message() {
+        let secret_key = SaplingKey::generate_key();
+        let public_address = secret_key.public_address();
+        let message = b"test message";
+
+        let signature = sign_message(&secret_key, message, thread_rng());
+        let wrong_message = b"another test message";
+        verify_message(&public_address, wrong_message, &signature)
+            .expect_err("verification should fail");
+    }
+
+    #[test]
+    fn verify_fails_with_wrong_public_address() {
+        let secret_key = SaplingKey::generate_key();
+        let message = b"test message";
+
+        let signature = sign_message(&secret_key, message, thread_rng());
+        let wrong_public_address = SaplingKey::generate_key().public_address();
+        verify_message(&wrong_public_address, message, &signature)
+            .expect_err("verification should fail");
+    }
+}