Support serde (#398)

* Implement serde for network messages.

* Make sure marker type implements serde.

* add serde support to all required structs

* use serdect

* gate under serde feature

* ci: add build with default features job

* add serde tests and required changes/fixes

* add support for encoding ciphersuite ID

---------

Co-authored-by: David Craven <[email protected]>

.github/workflows/main.yml

@@ -10,14 +10,26 @@ on:
 
 jobs:
 
+  build_default:
+    name: build with default features
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/[email protected]
+      - uses: actions-rs/[email protected]
+        with:
+          toolchain: beta
+          override: true
+      - uses: actions-rs/[email protected]
+        with:
+          command: build
+
   test_beta:
     name: test on beta
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/[email protected]
-      # Because we use nightly features for building docs,
-      # using --all-features will fail without nightly toolchain.
       - uses: actions-rs/[email protected]
         with:
           toolchain: beta

frost-core/CHANGELOG.md

@@ -7,6 +7,12 @@ Entries are listed in reverse chronological order.
 ## 0.5.0
 
 * add SigningShare type to ciphersuite libraries
+* most structs now have a private field which mean that they can no longer be
+  instantiated directly. `new()` methods have been added to them.
+* change `SigningPackage::new()` to take `&[u8]P  instead of `Vec<u8>`
+* expose `NonceCommitment` and `SignatureResponse` in ciphersuite crates
+* add `serde` support under `serde` feature to allow encoding structs which
+  need to be communicated between participants.
 
 ## Released
 

frost-core/Cargo.toml

@@ -22,6 +22,8 @@ debugless-unwrap = "0.0.4"
 digest = "0.10"
 hex = { version = "0.4.3", features = ["serde"] }
 rand_core = "0.6"
+serde = { version = "1.0.160", features = ["derive"], optional = true }
+serdect = { version = "0.2.0", optional = true }
 thiserror = "1.0"
 visibility = "0.0.1"
 zeroize = { version = "1.5.4", default-features = false, features = ["derive"] }
@@ -46,6 +48,7 @@ sha2 = "0.10.2"
 nightly = []
 default = []
 internals = []
+serde = ["dep:serde", "dep:serdect"]
 # Exposes ciphersuite-generic tests for other crates to use
 test-impl = ["proptest", "proptest-derive", "serde_json", "criterion"]
 

frost-core/src/benches.rs

@@ -146,7 +146,7 @@ pub fn bench_sign<C: Ciphersuite, R: RngCore + CryptoRng + Clone>(
 
         let message = "message to sign".as_bytes();
         let comms = commitments.clone().into_values().collect();
-        let signing_package = frost::SigningPackage::new(comms, message.to_vec());
+        let signing_package = frost::SigningPackage::new(comms, message);
 
         group.bench_with_input(
             BenchmarkId::new("Round 2", min_signers),

frost-core/src/frost.rs

@@ -183,7 +183,9 @@ fn derive_interpolating_value<C: Ciphersuite>(
 
 /// Generated by the coordinator of the signing operation and distributed to
 /// each signing party
-#[derive(Clone)]
+#[derive(Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(deny_unknown_fields))]
 pub struct SigningPackage<C: Ciphersuite> {
     /// The set of commitments participants published in the first round of the
     /// protocol.
@@ -192,26 +194,44 @@ pub struct SigningPackage<C: Ciphersuite> {
     ///
     /// Each signer should perform protocol-specific verification on the
     /// message.
+    #[cfg_attr(
+        feature = "serde",
+        serde(
+            serialize_with = "serdect::slice::serialize_hex_lower_or_bin",
+            deserialize_with = "serdect::slice::deserialize_hex_or_bin_vec"
+        )
+    )]
     message: Vec<u8>,
+    /// Ciphersuite ID for serialization
+    #[cfg_attr(
+        feature = "serde",
+        serde(serialize_with = "crate::ciphersuite_serialize::<_, C>")
+    )]
+    #[cfg_attr(
+        feature = "serde",
+        serde(deserialize_with = "crate::ciphersuite_deserialize::<_, C>")
+    )]
+    ciphersuite: (),
 }
 
 impl<C> SigningPackage<C>
 where
     C: Ciphersuite,
 {
-    /// Create a new `SigingPackage`
+    /// Create a new `SigningPackage`
     ///
     /// The `signing_commitments` are sorted by participant `identifier`.
     pub fn new(
         signing_commitments: Vec<round1::SigningCommitments<C>>,
-        message: Vec<u8>,
+        message: &[u8],
     ) -> SigningPackage<C> {
         SigningPackage {
             signing_commitments: signing_commitments
                 .into_iter()
                 .map(|s| (s.identifier, s))
                 .collect(),
-            message,
+            message: message.to_vec(),
+            ciphersuite: (),
         }
     }
 

frost-core/src/frost/identifier.rs

@@ -7,21 +7,26 @@ use std::{
 
 use crate::{Ciphersuite, Error, Field, FieldError, Group, Scalar};
 
+#[cfg(feature = "serde")]
+use crate::ScalarSerialization;
+
 /// A FROST participant identifier.
 ///
 /// The identifier is a field element in the scalar field that the secret polynomial is defined
 /// over, corresponding to some x-coordinate for a polynomial f(x) = y.  MUST NOT be zero in the
 /// field, as f(0) = the shared secret.
 #[derive(Copy, Clone, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(try_from = "ScalarSerialization<C>"))]
+#[cfg_attr(feature = "serde", serde(into = "ScalarSerialization<C>"))]
 pub struct Identifier<C: Ciphersuite>(Scalar<C>);
 
 impl<C> Identifier<C>
 where
     C: Ciphersuite,
 {
     /// Serialize the identifier using the ciphersuite encoding.
-    #[cfg_attr(feature = "internals", visibility::make(pub))]
-    pub(crate) fn serialize(&self) -> <<C::Group as Group>::Field as Field>::Serialization {
+    pub fn serialize(&self) -> <<C::Group as Group>::Field as Field>::Serialization {
         <<C::Group as Group>::Field>::serialize(&self.0)
     }
 
@@ -39,6 +44,28 @@ where
     }
 }
 
+#[cfg(feature = "serde")]
+impl<C> TryFrom<ScalarSerialization<C>> for Identifier<C>
+where
+    C: Ciphersuite,
+{
+    type Error = Error<C>;
+
+    fn try_from(value: ScalarSerialization<C>) -> Result<Self, Self::Error> {
+        Self::deserialize(&value.0)
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<C> From<Identifier<C>> for ScalarSerialization<C>
+where
+    C: Ciphersuite,
+{
+    fn from(value: Identifier<C>) -> Self {
+        Self(value.serialize())
+    }
+}
+
 impl<C> Eq for Identifier<C> where C: Ciphersuite {}
 
 impl<C> Debug for Identifier<C>