From e0ffd5227800d0dfa8a0f3fcc2a24e2a0003b665 Mon Sep 17 00:00:00 2001
From: Apoorv Darshan <ad13dtu@gmail.com>
Date: Thu, 9 Jul 2026 22:21:17 +0530
Subject: [PATCH] Raise ValueError from verify_digest for Edwards curve keys

VerifyingKey.verify_digest lacked the CurveEdTw guard that verify() and
the SigningKey.sign_digest* methods already have. Calling it on an EdDSA
(Ed25519/Ed448) key therefore fell through to the ECDSA path and raised a
confusing AttributeError: 'PublicKey' object has no attribute 'order',
instead of a clear error telling the user the method is unsupported.

Add the same guard used by sign_digest(), raising
ValueError("Method unsupported for Edwards curves"), and document the
raised exception. EdDSA signs the message directly and has no pre-hashed
digest API, so verify() is the correct entry point.

Fixes #349
---
 src/ecdsa/keys.py      |  5 +++++
 src/ecdsa/test_keys.py | 14 ++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/ecdsa/keys.py b/src/ecdsa/keys.py
index f74252c7..f17277c9 100644
--- a/src/ecdsa/keys.py
+++ b/src/ecdsa/keys.py
@@ -718,10 +718,15 @@ def verify_digest(
         :raises BadSignatureError: if the signature is invalid or malformed
         :raises BadDigestError: if the provided digest is too big for the curve
             associated with this VerifyingKey and allow_truncate was not set
+        :raises ValueError: if this is an Edwards curve key; use
+            :func:`~VerifyingKey.verify` instead, as EdDSA signs the message
+            directly and does not operate on pre-hashed digests
 
         :return: True if the verification was successful
         :rtype: bool
         """
+        if isinstance(self.curve.curve, CurveEdTw):
+            raise ValueError("Method unsupported for Edwards curves")
         # signature doesn't have to be a bytes-like-object so don't normalise
         # it, the decoders will do that
         digest = normalise_bytes(digest)
diff --git a/src/ecdsa/test_keys.py b/src/ecdsa/test_keys.py
index 348475e2..2bad8876 100644
--- a/src/ecdsa/test_keys.py
+++ b/src/ecdsa/test_keys.py
@@ -438,6 +438,20 @@ def test_ed25519_sig_verify_malformed(self):
         with self.assertRaises(BadSignatureError):
             vk.verify(sig, data)
 
+    def test_ed25519_verify_digest(self):
+        vk_pem = (
+            "-----BEGIN PUBLIC KEY-----\n"
+            "MCowBQYDK2VwAyEAIwBQ0NZkIiiO41WJfm5BV42u3kQm7lYnvIXmCy8qy2U=\n"
+            "-----END PUBLIC KEY-----\n"
+        )
+
+        vk = VerifyingKey.from_pem(vk_pem)
+
+        with self.assertRaises(ValueError) as e:
+            vk.verify_digest(b"a" * 64, b"b" * 32)
+
+        self.assertIn("Method unsupported for Edwards", str(e.exception))
+
     def test_ed448_from_pem(self):
         pem_str = (
             "-----BEGIN PUBLIC KEY-----\n"