def verify(msg, sig, pk):
"verify a 256-bit value using hash-bash signatures"
msg = crypturd.fixed_length_key(msg, 32)
checksum = 0
digest = ""
for i in range(32):
c = ord(msg[i])
checksum += c
digest += hash_times(sig[i * 32:i * 32 + 32], 256 - c)
digest += hash_times(sig[-64:-32], checksum // 256)
digest += hash_times(sig[-32:], checksum % 256)
return sha256(digest) == pk
def sign(msg, sk):
"Sign a 256-bit value"
msg = crypturd.fixed_length_key(msg, 32)
sig = ""
checksum = 0
for i in range(32):
c = ord(msg[i])
checksum += c
sig += hash_times(sk[i * 32:i * 32 + 32], c)
# sign a checksum
sig += hash_times(sk[-64:-32], 32 - (checksum // 256))
sig += hash_times(sk[-32:], 256 - (checksum % 256))
return sig
def sign_right(msg2, sk):
"Sign 2 256-bit values using hash-bash signatures (second part)"
msg2 = crypturd.fixed_length_key(msg2, 32)
sig = ""
M2 = crypturd.bigendian2int(msg2)
for i in range(256):
zero = sk[i * 64 + 16384:i * 64 + 16416]
one = sk[i * 64 + 16416:i * 64 + 16448]
if ((1 << i) & M2) > 0:
zero = crypturd.sha256(zero)
else:
one = crypturd.sha256(one)
sig += zero + one
return sig
def sign_left(msg1, sk):
"Sign 2 256-bit values using hash-bash signatures (first part)"
msg1 = crypturd.fixed_length_key(msg1, 32)
M1 = crypturd.bigendian2int(msg1)
sig = ""
for i in range(256):
zero = sk[i * 64:i * 64 + 32]
one = sk[i * 64 + 32:i * 64 + 64]
if ((1 << i) & M1) > 0:
zero = crypturd.sha256(zero)
else:
one = crypturd.sha256(one)
sig += zero + one
return sig
def digest_right(msg2, sig):
"verify 2 256-bit values using hash-bash signatures (second part)"
msg1 = crypturd.fixed_length_key(msg2, 32)
digest2 = ""
M2 = crypturd.bigendian2int(msg2)
for i in range(256):
zero = sig[i * 64 + 16384:i * 64 + 16416]
one = sig[i * 64 + 16416:i * 64 + 16448]
if ((1 << i) & M2) > 0:
one = crypturd.sha256(one)
else:
zero = crypturd.sha256(zero)
digest2 += zero + one
return sha256(digest2)
def digest_left(msg1, sig):
"verify 2 256-bit values using hash-bash signatures (first part)"
msg1 = crypturd.fixed_length_key(msg1, 32)
digest1 = ""
M1 = crypturd.bigendian2int(msg1)
for i in range(256):
zero = sig[i * 64:i * 64 + 32]
one = sig[i * 64 + 32:i * 64 + 64]
if ((1 << i) & M1) > 0:
one = crypturd.sha256(one)
else:
zero = crypturd.sha256(zero)
digest1 += zero + one
return sha256(digest1)