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Add is_quad function to bip-schnorr reference code

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This commit is contained in:
Jonas Nick 2019-09-27 09:56:21 +00:00
parent 5c52872fe0
commit 1882aa7b8f
1 changed files with 6 additions and 3 deletions
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9
bip-schnorr/reference.py
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@ -62,6 +62,9 @@ def hash_sha256(b):
def jacobi(x):
return pow(x, (p - 1) // 2, p)
def is_quad(x):
return jacobi(x) == 1
def pubkey_gen(seckey):
P = point_mul(G, seckey)
return bytes_from_point(P)
@ -72,12 +75,12 @@ def schnorr_sign(msg, seckey0):
if not (1 <= seckey0 <= n - 1):
raise ValueError('The secret key must be an integer in the range 1..n-1.')
P = point_mul(G, seckey0)
seckey = seckey0 if (jacobi(y(P)) == 1) else n - seckey0
seckey = seckey0 if is_quad(y(P)) else n - seckey0
k0 = int_from_bytes(tagged_hash("BIPSchnorrDerive", bytes_from_int(seckey) + msg)) % n
if k0 == 0:
raise RuntimeError('Failure. This happens only with negligible probability.')
R = point_mul(G, k0)
k = n - k0 if (jacobi(y(R)) != 1) else k0
k = n - k0 if not is_quad(y(R)) else k0
e = int_from_bytes(tagged_hash("BIPSchnorr", bytes_from_point(R) + bytes_from_point(P) + msg)) % n
return bytes_from_point(R) + bytes_from_int((k + e * seckey) % n)
@ -97,7 +100,7 @@ def schnorr_verify(msg, pubkey, sig):
return False
e = int_from_bytes(tagged_hash("BIPSchnorr", sig[0:32] + pubkey + msg)) % n
R = point_add(point_mul(G, s), point_mul(P, n - e))
if R is None or jacobi(y(R)) != 1 or x(R) != r:
if R is None or not is_quad(y(R)) or x(R) != r:
return False
return True