Add ecdsa Python library.

bin/python/ecdsa/rfc6979.py

@@ -0,0 +1,103 @@
+'''
+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):
+    '''
+        generator - 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()