Impld secp256k1 DHKEX; doesn't work with serde for some reason

.github/workflows/ci.yml

@@ -31,6 +31,12 @@ jobs:
           toolchain: ${{ matrix.toolchain }}
           override: true
 
+      - name: Run cargo test with just K256 and serde enabled
+        env:
+          CARGO_INCREMENTAL: 0
+          RUSTFLAGS: -D warnings -A dead_code -A unused_imports
+        run: cargo test --no-default-features --features="k256,serde_impls"
+
       - name: Run cargo test with just X25519 enabled
         env:
           CARGO_INCREMENTAL: 0

Cargo.toml

@@ -19,8 +19,9 @@ default = ["alloc", "p256", "x25519"]
 x25519 = ["dep:x25519-dalek"]
 p384 = ["dep:p384"]
 p256 = ["dep:p256"]
+k256 = ["dep:k256"]
 # Include serde Serialize/Deserialize impls for all relevant types
-serde_impls = ["serde", "generic-array/serde"]
+serde_impls = ["dep:serde", "generic-array/serde", "x25519-dalek?/serde", "p256?/serde", "p384?/serde", "k256?/serde", "p256?/pkcs8", "p384?/pkcs8", "k256?/pkcs8"]
 # Include allocating methods like open() and seal()
 alloc = []
 # Includes an implementation of `std::error::Error` for `HpkeError`. Also does what `alloc` does.
@@ -36,6 +37,7 @@ digest = "0.10"
 hkdf = "0.12"
 hmac = "0.12"
 rand_core = { version = "0.6", default-features = false }
+k256 = { version = "0.13", default-features = false, features = ["arithmetic", "ecdh"], optional = true}
 p256 = { version = "0.13", default-features = false, features = ["arithmetic", "ecdh"], optional = true}
 p384 = { version = "0.13", default-features = false, features = ["arithmetic", "ecdh"], optional = true}
 sha2 = { version = "0.10", default-features = false }

src/dhkex.rs

@@ -72,7 +72,7 @@ pub trait DhKeyExchange {
     ) -> (Self::PrivateKey, Self::PublicKey);
 }
 
-#[cfg(any(feature = "p256", feature = "p384"))]
+#[cfg(any(feature = "p256", feature = "p384", feature = "k256"))]
 pub(crate) mod ecdh_nistp;
 
 #[cfg(feature = "x25519")]

src/dhkex/ecdh_nistp.rs

@@ -259,6 +259,17 @@ nistp_dhkex!(
     0xFF          // RFC 9180 §7.1.3: The `bitmask` in DeriveKeyPair to be 0xFF for P-384
 );
 
+#[cfg(feature = "k256")]
+nistp_dhkex!(
+    "K-256",
+    DhK256,
+    k256,
+    typenum::U65,
+    typenum::U32,
+    typenum::U32,
+    0xFF
+);
+
 #[cfg(test)]
 mod tests {
     use crate::{dhkex::DhKeyExchange, test_util::dhkex_gen_keypair, Deserializable, Serializable};