ed25519: optional zerocopy dependency (#1134)

Derives trait impls for `Signature` and `PublicKeyBytes`

Cargo.lock

@@ -407,6 +407,7 @@ dependencies = [
  "serde",
  "serde_bytes",
  "signature",
+ "zerocopy",
  "zeroize",
 ]
 

ed25519/Cargo.toml

@@ -25,6 +25,7 @@ pkcs8 = { version = "0.11.0-rc.8", optional = true }
 serde = { version = "1", optional = true, default-features = false }
 serde_bytes = { version = "0.11", optional = true, default-features = false }
 zeroize = { version = "1", optional = true, default-features = false }
+zerocopy = { version = "0.8", optional = true, features = ["derive"] }
 
 [dev-dependencies]
 #ed25519-dalek = { version = "2", features = ["rand_core"] }

ed25519/src/lib.rs

@@ -296,6 +296,9 @@ use pkcs8::spki::{
 #[cfg(feature = "zeroize")]
 use zeroize::Zeroize;
 
+#[cfg(feature = "zerocopy")]
+use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout, Unaligned};
+
 /// Size of a single component of an Ed25519 signature.
 const COMPONENT_SIZE: usize = 32;
 
@@ -314,6 +317,10 @@ pub type SignatureBytes = [u8; Signature::BYTE_SIZE];
 /// Signature verification libraries are expected to reject invalid field
 /// elements at the time a signature is verified.
 #[derive(Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(
+    feature = "zerocopy",
+    derive(FromBytes, IntoBytes, Immutable, KnownLayout, Unaligned)
+)]
 #[repr(C)]
 pub struct Signature {
     R: ComponentBytes,

ed25519/src/pkcs8.rs

@@ -35,6 +35,9 @@ use core::str;
 #[cfg(feature = "zeroize")]
 use zeroize::Zeroize;
 
+#[cfg(feature = "zerocopy")]
+use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout, Unaligned};
+
 /// Algorithm [`ObjectIdentifier`] for the Ed25519 digital signature algorithm
 /// (`id-Ed25519`).
 ///
@@ -226,6 +229,11 @@ impl str::FromStr for KeypairBytes {
 /// Note that this type operates on raw bytes and performs no validation that
 /// public keys represent valid compressed Ed25519 y-coordinates.
 #[derive(Clone, Copy, Eq, PartialEq)]
+#[cfg_attr(
+    feature = "zerocopy",
+    derive(IntoBytes, FromBytes, Unaligned, KnownLayout, Immutable,)
+)]
+#[repr(transparent)]
 pub struct PublicKeyBytes(pub [u8; Self::BYTE_SIZE]);
 
 impl PublicKeyBytes {