Serialization x25519 (#4688)

* modify x25519 serialization to match x448

supports raw and pkcs8 encoding on private_bytes
supports raw and subjectpublickeyinfo on public_bytes

deprecates zero argument call to public_bytes

* add docs

* this is public now

* don't need that

* review feedback

1 files changed, 8 insertions, 2 deletions

diff --git a/src/cryptography/hazmat/primitives/asymmetric/x25519.py b/src/cryptography/hazmat/primitives/asymmetric/x25519.py
index f4bdf3db..94602261 100644
--- a/src/cryptography/hazmat/primitives/asymmetric/x25519.py
+++ b/src/cryptography/hazmat/primitives/asymmetric/x25519.py
@@ -28,7 +28,7 @@ class X25519PublicKey(object):
         return backend.x25519_load_public_bytes(data)
 
     @abc.abstractmethod
-    def public_bytes(self):
+    def public_bytes(self, encoding=None, format=None):
         """
         The serialized bytes of the public key.
         """
@@ -47,7 +47,7 @@ class X25519PrivateKey(object):
         return backend.x25519_generate_key()
 
     @classmethod
-    def _from_private_bytes(cls, data):
+    def from_private_bytes(cls, data):
         from cryptography.hazmat.backends.openssl.backend import backend
         return backend.x25519_load_private_bytes(data)
 
@@ -58,6 +58,12 @@ class X25519PrivateKey(object):
         """
 
     @abc.abstractmethod
+    def private_bytes(self, encoding, format, encryption_algorithm):
+        """
+        The serialized bytes of the private key.
+        """
+
+    @abc.abstractmethod
     def exchange(self, peer_public_key):
         """
         Performs a key exchange operation using the provided peer's public key.