Resolve #94 (#109)

* semantically finished

* `fmt`

* Update Cargo.toml

version bump

rust-k256/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "plume_rustcrypto"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2021"
 license = "MIT"
 description = "Implementation of PLUME: nullifier friendly signature scheme on ECDSA; using the k256 library"
@@ -17,7 +17,12 @@ num-bigint = "~0.4.3"
 num-integer = "~0.1.45"
 k256 = {version = "~0.13.3", features = ["arithmetic", "hash2curve", "expose-field", "sha2"]}
 signature = "^2.2.0"
+serde = { version = "^1.0.0", features = ["derive"], optional = true }
 
 [dev-dependencies]
 hex = "0.4.3"
-hex-literal = "0.3.4"
+hex-literal = "0.3.4"
+
+[features]
+default = ["serde"]
+serde = ["dep:serde", "k256/serde"]

rust-k256/src/lib.rs

@@ -44,6 +44,10 @@ pub use k256::{AffinePoint, NonZeroScalar, SecretKey};
 /// Re-exports the [`CryptoRngCore`] trait from the [`rand_core`] crate.
 /// This allows it to be used from the current module.
 pub use rand_core::CryptoRngCore;
+#[cfg(feature = "serde")]
+/// Provides the ability to serialize and deserialize data using the Serde library.
+/// The `Serialize` and `Deserialize` traits from the Serde library are re-exported for convenience.
+pub use serde::{Deserialize, Serialize};
 
 mod utils;
 // not published due to use of `Projective...`; these utils can be found in other crates
@@ -59,6 +63,7 @@ pub const DST: &[u8] = b"QUUX-V01-CS02-with-secp256k1_XMD:SHA-256_SSWU_RO_"; //
 /// Struct holding signature data for a PLUME signature.
 ///
 /// `v1specific` field differintiate whether V1 or V2 protocol will be used.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct PlumeSignature {
     /// The message that was signed.
     pub message: Vec<u8>,
@@ -75,6 +80,7 @@ pub struct PlumeSignature {
 }
 /// Nested struct holding additional signature data used in variant 1 of the protocol.
 #[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct PlumeSignatureV1Fields {
     /// Part of the signature data, a curve point.  
     pub r_point: AffinePoint,

rust-k256/src/randomizedsigner.rs

@@ -15,10 +15,13 @@ use k256::{
 use signature::{Error, RandomizedSigner};
 
 /// `PlumeSigner` is a `struct` that contains a reference to a secret key and a
-/// boolean defining output [`PlumeSignature`] variant. It implements the
-/// `RandomizedSigner` trait to generate signatures using the provided secret
-/// key. The struct is generic over the lifetime of the secret key reference
-/// so that the key can be borrowed immutably.
+/// boolean defining output [`PlumeSignature`] variant.
+///
+/// It implements the `RandomizedSigner` trait to generate signatures using the provided secret
+/// key. The struct is generic over the lifetime of the secret key reference so that the key can be borrowed immutably.
+///
+/// `serde` traits aren't added to this struct on purpose. It's a wrapper around [`SecretKey`] which provides variety of serialization formats (SEC1, bytes, ...).
+/// Also it uses just a reference to the secret key itself, so the choices for handling the key is kept open here.
 pub struct PlumeSigner<'signing> {
     /// The secret key to use for signing. This is borrowed immutably.
     secret_key: &'signing SecretKey,