Source code for pycoin.ecdsa.rfc6979

import hashlib
import hmac

from . import intstream

if hasattr(1, "bit_length"):
    def bit_length(v):
        "the ``int.bit_length`` in `python 3 <>`_"
        return v.bit_length()
[docs] def bit_length(self): "the ``int.bit_length`` in `python 3 <>`_" # compared to "while n>0: bl +=1 ; n >>= 1", this is much faster in both python2 and pypy # code taken from the link above s = bin(self) # binary representation: bin(-37) --> '-0b100101' s = s.lstrip('-0b') # remove leading zeros and minus sign return len(s) # len('100101') --> 6
[docs]def deterministic_generate_k(generator_order, secret_exponent, val, hash_f=hashlib.sha256): """ :param generator_order: result from `pycoin.ecdsa.Generator.Generator.order`, necessary to ensure the k value is within bound :param secret_exponent: an integer secret_exponent to generate the k value for :param val: the value to be signed, also used as an entropy source for the k value :returns: an integer k such that ``1 <= k < generator_order``, complying with <> """ n = generator_order bln = bit_length(n) order_size = (bln + 7) // 8 hash_size = hash_f().digest_size v = b'\x01' * hash_size k = b'\x00' * hash_size priv = intstream.to_bytes(secret_exponent, length=order_size) shift = 8 * hash_size - bln if shift > 0: val >>= shift if val >= n: val -= n h1 = intstream.to_bytes(val, length=order_size) k =, v + b'\x00' + priv + h1, hash_f).digest() v =, v, hash_f).digest() k =, v + b'\x01' + priv + h1, hash_f).digest() v =, v, hash_f).digest() while 1: t = bytearray() while len(t) < order_size: v =, v, hash_f).digest() t.extend(v) k1 = intstream.from_bytes(bytes(t)) k1 >>= (len(t)*8 - bln) if k1 >= 1 and k1 < n: return k1 k =, v + b'\x00', hash_f).digest() v =, v, hash_f).digest()
""" Some portions adapted from Copyright (c) 2010 Brian Warner who granted its use under this license: Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Portions written in 2005 by Peter Pearson and placed in the public domain. """