ed25519: implement SignatureBitStringEncoding support (#889)

ed25519/src/lib.rs

@@ -273,13 +273,25 @@ mod serde;
 pub use signature::{self, Error, SignatureEncoding};
 
 #[cfg(feature = "pkcs8")]
-pub use crate::pkcs8::{KeypairBytes, PublicKeyBytes};
+pub use crate::pkcs8::{
+    spki::{
+        der::{oid::ObjectIdentifier, AnyRef},
+        AlgorithmIdentifierRef, AssociatedAlgorithmIdentifier,
+    },
+    KeypairBytes, PublicKeyBytes,
+};
 
 use core::fmt;
 
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
 
+#[cfg(all(feature = "alloc", feature = "pkcs8"))]
+use pkcs8::spki::{
+    der::{self, asn1::BitString},
+    SignatureBitStringEncoding,
+};
+
 /// Size of a single component of an Ed25519 signature.
 const COMPONENT_SIZE: usize = 32;
 
@@ -371,6 +383,23 @@ impl SignatureEncoding for Signature {
     }
 }
 
+#[cfg(all(feature = "alloc", feature = "pkcs8"))]
+impl SignatureBitStringEncoding for Signature {
+    fn to_bitstring(&self) -> der::Result<BitString> {
+        BitString::new(0, self.to_vec())
+    }
+}
+
+#[cfg(feature = "pkcs8")]
+impl AssociatedAlgorithmIdentifier for Signature {
+    type Params = AnyRef<'static>;
+
+    const ALGORITHM_IDENTIFIER: AlgorithmIdentifierRef<'static> = AlgorithmIdentifierRef {
+        oid: ObjectIdentifier::new_unwrap("1.3.101.112"),
+        parameters: None,
+    };
+}
+
 impl From<Signature> for SignatureBytes {
     fn from(sig: Signature) -> SignatureBytes {
         sig.to_bytes()