core: implement ssz for all objects with tests (#14)

* core: implement ssz for all objects with tests

* clippy

* wip serializable objects

* fix visibility

* simplify by rm macro

* simplify testing

Author: tcoratger

src/array.rs

@@ -3,6 +3,7 @@ use ssz::{Decode, DecodeError, Encode};
 use std::ops::{Deref, DerefMut};
 
 use crate::F;
+use crate::serialization::Serializable;
 use p3_field::{PrimeCharacteristicRing, PrimeField32, RawDataSerializable};
 
 /// A wrapper around an array of field elements that implements SSZ Encode/Decode.
@@ -86,6 +87,8 @@ impl<const N: usize> Decode for FieldArray<N> {
     }
 }
 
+impl<const N: usize> Serializable for FieldArray<N> {}
+
 impl<const N: usize> Serialize for FieldArray<N> {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where

src/inc_encoding.rs

@@ -1,8 +1,8 @@
 use rand::Rng;
-use serde::{Serialize, de::DeserializeOwned};
 use std::fmt::Debug;
 
 use crate::MESSAGE_LENGTH;
+use crate::serialization::Serializable;
 
 /// Trait to model incomparable encoding schemes.
 /// These schemes allow to encode a message into a codeword.
@@ -17,8 +17,8 @@ use crate::MESSAGE_LENGTH;
 /// x = (x_1,..,x_k) and x' = (x'_1,..,x'_k) we have
 /// x_i > x'_i for all i = 1,...,k.
 pub trait IncomparableEncoding {
-    type Parameter: Serialize + DeserializeOwned;
-    type Randomness: Serialize + DeserializeOwned;
+    type Parameter: Serializable;
+    type Randomness: Serializable;
     type Error: Debug;
 
     /// number of entries in a codeword

src/lib.rs

@@ -17,6 +17,7 @@ pub(crate) type PackedF = <F as Field>::Packing;
 pub(crate) mod array;
 pub(crate) mod hypercube;
 pub(crate) mod inc_encoding;
+pub mod serialization;
 pub mod signature;
 pub(crate) mod simd_utils;
 pub(crate) mod symmetric;

src/serialization.rs

@@ -0,0 +1,45 @@
+//! A unified serialization implementation
+
+use serde::{Serialize, de::DeserializeOwned};
+use ssz::{Decode, DecodeError, Encode};
+
+/// A supertrait combining all serialization capabilities needed for leanSig types.
+pub trait Serializable: Serialize + DeserializeOwned + Encode + Decode + Sized {
+    /// Converts this object to a canonical byte representation.
+    ///
+    /// # Canonical Format
+    ///
+    /// - All field elements are converted to canonical `u32` form (not Montgomery)
+    /// - All `u32` values are encoded as 4 bytes in little-endian order
+    ///
+    /// # Returns
+    ///
+    /// A `Vec<u8>` containing the canonical byte representation of this object.
+    fn to_bytes(&self) -> Vec<u8> {
+        // TODO: Update this to not use SSZ internally.
+        self.as_ssz_bytes()
+    }
+
+    /// Parses an object from its canonical byte representation.
+    ///
+    /// # Canonical Format
+    ///
+    /// The input bytes must follow the same canonical format as `to_bytes()`:
+    /// - Field elements as canonical `u32` values (4 bytes, little-endian)
+    /// - Composite structures following SSZ layout rules
+    ///
+    /// # Arguments
+    ///
+    /// * `bytes` - The canonical binary data to parse
+    ///
+    /// # Returns
+    ///
+    /// - `Ok(Self)` if the bytes represent a valid object
+    /// - `Err(DecodeError)` if the bytes are malformed or invalid
+    fn from_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        // TODO: Update this to not use SSZ internally.
+        Self::from_ssz_bytes(bytes)
+    }
+}
+
+impl Serializable for [u8; 32] {}

src/signature.rs

@@ -1,9 +1,8 @@
 use std::ops::Range;
 
 use crate::MESSAGE_LENGTH;
+use crate::serialization::Serializable;
 use rand::Rng;
-use serde::{Serialize, de::DeserializeOwned};
-use ssz::{Decode, Encode};
 use thiserror::Error;
 
 /// Error enum for the signing process.
@@ -99,17 +98,21 @@ pub trait SignatureScheme {
     /// The key must be serializable to allow for network transmission and storage.
     ///
     /// We must support SSZ encoding for Ethereum consensus layer compatibility.
-    type PublicKey: Serialize + DeserializeOwned + Encode + Decode;
+    type PublicKey: Serializable;
 
     /// The secret key used for signing.
     ///
     /// The key must be serializable for persistence and secure backup.
-    type SecretKey: SignatureSchemeSecretKey + Serialize + DeserializeOwned;
+    ///
+    /// We must support SSZ encoding for Ethereum consensus layer compatibility.
+    type SecretKey: SignatureSchemeSecretKey + Serializable;
 
     /// The signature object produced by the signing algorithm.
     ///
     /// The signature must be serializable to allow for network transmission and storage.
-    type Signature: Serialize + DeserializeOwned;
+    ///
+    /// We must support SSZ encoding for Ethereum consensus layer compatibility.
+    type Signature: Serializable;
 
     /// The maximum number of epochs supported by this signature scheme configuration,
     /// denoted as $L$ in the literature [DKKW25a, DKKW25b].