return curve.exp(prv)
-def sign(curve, prv, digest, mode=2001):
+def sign(curve, prv, digest, rand=None, mode=2001):
""" Calculate signature for provided digest
:param GOST3410Curve curve: curve to use
:param long prv: private key
:param digest: digest for signing
:type digest: bytes, 32 or 64 bytes
+ :param rand: optional predefined random data used for k/r generation
+ :type rand: bytes, 32 or 64 bytes
:returns: signature
:rtype: bytes, 64 or 128 bytes
"""
if e == 0:
e = 1
while True:
- k = bytes2long(urandom(size)) % q
+ if rand is None:
+ rand = urandom(size)
+ elif len(rand) != size:
+ raise ValueError("rand length != %d" % size)
+ k = bytes2long(rand) % q
if k == 0:
continue
r, _ = curve.exp(k)