/usr/lib/python2.7/dist-packages/ecdsa/rfc6979.py is in python-ecdsa 0.13-2.
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RFC 6979:
Deterministic Usage of the Digital Signature Algorithm (DSA) and
Elliptic Curve Digital Signature Algorithm (ECDSA)
http://tools.ietf.org/html/rfc6979
Many thanks to Coda Hale for his implementation in Go language:
https://github.com/codahale/rfc6979
'''
import hmac
from binascii import hexlify
from .util import number_to_string, number_to_string_crop
from six import b
try:
bin(0)
except NameError:
binmap = {"0": "0000", "1": "0001", "2": "0010", "3": "0011",
"4": "0100", "5": "0101", "6": "0110", "7": "0111",
"8": "1000", "9": "1001", "a": "1010", "b": "1011",
"c": "1100", "d": "1101", "e": "1110", "f": "1111"}
def bin(value): # for python2.5
v = "".join(binmap[x] for x in "%x"%abs(value)).lstrip("0")
if value < 0:
return "-0b" + v
return "0b" + v
def bit_length(num):
# http://docs.python.org/dev/library/stdtypes.html#int.bit_length
s = bin(num) # binary representation: bin(-37) --> '-0b100101'
s = s.lstrip('-0b') # remove leading zeros and minus sign
return len(s) # len('100101') --> 6
def bits2int(data, qlen):
x = int(hexlify(data), 16)
l = len(data) * 8
if l > qlen:
return x >> (l-qlen)
return x
def bits2octets(data, order):
z1 = bits2int(data, bit_length(order))
z2 = z1 - order
if z2 < 0:
z2 = z1
return number_to_string_crop(z2, order)
# https://tools.ietf.org/html/rfc6979#section-3.2
def generate_k(order, secexp, hash_func, data):
'''
order - order of the DSA generator used in the signature
secexp - secure exponent (private key) in numeric form
hash_func - reference to the same hash function used for generating hash
data - hash in binary form of the signing data
'''
qlen = bit_length(order)
holen = hash_func().digest_size
rolen = (qlen + 7) / 8
bx = number_to_string(secexp, order) + bits2octets(data, order)
# Step B
v = b('\x01') * holen
# Step C
k = b('\x00') * holen
# Step D
k = hmac.new(k, v+b('\x00')+bx, hash_func).digest()
# Step E
v = hmac.new(k, v, hash_func).digest()
# Step F
k = hmac.new(k, v+b('\x01')+bx, hash_func).digest()
# Step G
v = hmac.new(k, v, hash_func).digest()
# Step H
while True:
# Step H1
t = b('')
# Step H2
while len(t) < rolen:
v = hmac.new(k, v, hash_func).digest()
t += v
# Step H3
secret = bits2int(t, qlen)
if secret >= 1 and secret < order:
return secret
k = hmac.new(k, v+b('\x00'), hash_func).digest()
v = hmac.new(k, v, hash_func).digest()
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