fix: more efficient kid derivation

Signed-off-by: Daniel Bluhm <dbluhm@pm.me>

Author: dbluhm

didcomm_messaging/crypto/backend/askar.py

@@ -116,6 +116,11 @@ def multikey(self) -> str:
         """Get the key in multibase format."""
         return self._multikey
 
+    @property
+    def key_bytes(self) -> bytes:
+        """Get the bytes of the key."""
+        return self.key.get_public_bytes()
+
 
 class AskarSecretKey(SecretKey):
     """Secret key implementation for Askar."""

didcomm_messaging/crypto/backend/authlib.py

@@ -56,6 +56,18 @@ def multikey(self) -> str:
         """Return the key in multikey format."""
         return self._multikey
 
+    @property
+    def key_bytes(self) -> bytes:
+        """Get the bytes of the key."""
+        jwk = self.key.as_dict(is_private=False)
+        codec = self.kty_crv_to_codec.get((jwk["kty"], jwk.get("crv")))
+
+        if not codec:
+            raise ValueError("Unsupported key type")
+
+        key_bytes = b64url.decode(jwk["x"])
+        return key_bytes
+
     @classmethod
     def key_to_multikey(cls, key: AsymmetricKey) -> str:
         """Convert an Authlib key to a multikey."""

didcomm_messaging/crypto/base.py

@@ -69,6 +69,11 @@ def kid(self) -> str:
     def multikey(self) -> str:
         """Get the key in multikey format."""
 
+    @property
+    @abstractmethod
+    def key_bytes(self) -> bytes:
+        """Get the bytes of the key."""
+
 
 class SecretKey(ABC):
     """Secret Key Type."""

didcomm_messaging/legacy/messaging.py

@@ -12,7 +12,6 @@
 from didcomm_messaging.crypto import P, S, SecretsManager
 from didcomm_messaging.legacy.base import LegacyCryptoService
 from didcomm_messaging.legacy.packaging import LegacyPackagingService
-from didcomm_messaging.multiformats import multibase, multicodec
 from didcomm_messaging.resolver import DIDResolver
 
 
@@ -59,13 +58,6 @@ class Target:
 class LegacyDIDCommMessagingService(Generic[P, S]):
     """Main entrypoint for DIDComm Messaging."""
 
-    def multikey_to_kid(self, multikey: str) -> str:
-        """Return a kid from a multikey."""
-        codec, data = multicodec.unwrap(multibase.decode(multikey))
-        if codec != multicodec.multicodec("ed25519-pub"):
-            raise LegacyDIDCommMessagingError("DIDComm v1 requires ed25519 keys")
-        return base58.b58encode(data).decode()
-
     async def did_to_target(
         self, crypto: LegacyCryptoService[P, S], resolver: DIDResolver, did: str
     ) -> Target:
@@ -81,19 +73,19 @@ async def did_to_target(
         target = services[0]
 
         recipient_keys = [
-            self.multikey_to_kid(
+            base58.b58encode(
                 crypto.verification_method_to_public_key(
                     doc.dereference_as(VerificationMethod, recip)
-                ).multikey
-            )
+                ).key_bytes
+            ).decode()
             for recip in target.recipient_keys
         ]
         routing_keys = [
-            self.multikey_to_kid(
+            base58.b58encode(
                 crypto.verification_method_to_public_key(
                     doc.dereference_as(VerificationMethod, routing_key)
-                ).multikey
-            )
+                ).key_bytes
+            ).decode()
             for routing_key in target.routing_keys
         ]
         endpoint = target.service_endpoint
@@ -121,11 +113,11 @@ async def from_did_to_kid(
         target = services[0]
 
         recipient_keys = [
-            self.multikey_to_kid(
+            base58.b58encode(
                 crypto.verification_method_to_public_key(
                     doc.dereference_as(VerificationMethod, recip)
-                ).multikey
-            )
+                ).key_bytes
+            ).decode()
             for recip in target.recipient_keys
         ]
         return recipient_keys[0]

didcomm_messaging/legacy/nacl.py

@@ -69,6 +69,11 @@ def multikey(self) -> str:
             multicodec.wrap("ed25519-pub", base58.b58decode(self.key)), "base58btc"
         )
 
+    @property
+    def key_bytes(self) -> bytes:
+        """Get the bytes of the key."""
+        return self.value
+
 
 class NaclLegacyCryptoService(LegacyCryptoService[EdPublicKey, KeyPair]):
     """Legacy crypto service using pynacl."""