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Fix CVE-2024-23342 and PVE-2024-64396: Enhance timing attack resistance in ECDSA operations #365

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Fix CVE-2024-23342 and PVE-2024-64396: Enhance timing attack resistance in ECDSA operations #365

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1f5b902
fix CVE-2024-23342 and PVE-2024-64396: Enhance timing attack resistan…
alexandrehpiva Sep 15, 2025
226b375
optimize ECDSA sign method avoiding unnecessary point multiplications
alexandrehpiva Sep 15, 2025
f9bfe7e
fix entropy test by replacing predictable entropy pattern with proper…
alexandrehpiva Sep 15, 2025
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15 changes: 7 additions & 8 deletions src/ecdsa/ecdsa.py
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Original file line number Diff line number Diff line change
Expand Up @@ -249,22 +249,21 @@ def sign(self, hash, random_k):
G = self.public_key.generator
n = G.order()
k = random_k % n
# Fix the bit-length of the random nonce,
# so that it doesn't leak via timing.
# This does not change that ks = k mod n
n_bits = bit_length(n)
ks = k + n
kt = ks + n
if bit_length(ks) == bit_length(n):
if bit_length(ks) == n_bits:
p1 = kt * G
else:
p1 = ks * G
r = p1.x() % n
if r == 0:
raise RSZeroError("amazingly unlucky random number r")
s = (
numbertheory.inverse_mod(k, n)
* (hash + (self.secret_multiplier * r) % n)
) % n
hash_mod = hash % n
secret_r = (self.secret_multiplier * r) % n
s_input = (hash_mod + secret_r) % n
k_inv = numbertheory.inverse_mod(k, n)
s = (k_inv * s_input) % n
if s == 0:
raise RSZeroError("amazingly unlucky random number s")
return Signature(r, s)
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