Add explicit exception if we are missing a deserializer

libp2p/crypto/exceptions.py

@@ -0,0 +1,14 @@
+from libp2p.exceptions import BaseLibp2pError
+
+
+class CryptographyError(BaseLibp2pError):
+    pass
+
+
+class MissingDeserializerError(CryptographyError):
+    """
+    Raise if the requested deserialization routine is missing for
+    some type of cryptographic key.
+    """
+
+    pass

libp2p/crypto/serialization.py

@@ -1,4 +1,5 @@
 from libp2p.crypto.ed25519 import Ed25519PublicKey
+from libp2p.crypto.exceptions import MissingDeserializerError
 from libp2p.crypto.keys import KeyType, PrivateKey, PublicKey
 from libp2p.crypto.rsa import RSAPublicKey
 from libp2p.crypto.secp256k1 import Secp256k1PrivateKey, Secp256k1PublicKey
@@ -16,11 +17,17 @@ key_type_to_private_key_deserializer = {
 
 def deserialize_public_key(data: bytes) -> PublicKey:
     f = PublicKey.deserialize_from_protobuf(data)
-    deserializer = key_type_to_public_key_deserializer[f.key_type]
+    try:
+        deserializer = key_type_to_public_key_deserializer[f.key_type]
+    except KeyError:
+        raise MissingDeserializerError({"key_type": f.key_type, "key": "public_key"})
     return deserializer(f.data)
 
 
 def deserialize_private_key(data: bytes) -> PrivateKey:
     f = PrivateKey.deserialize_from_protobuf(data)
-    deserializer = key_type_to_private_key_deserializer[f.key_type]
+    try:
+        deserializer = key_type_to_private_key_deserializer[f.key_type]
+    except KeyError:
+        raise MissingDeserializerError({"key_type": f.key_type, "key": "private_key"})
     return deserializer(f.data)