found hashcash implementation

hashcash.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python
+"""
+Module to generate and validate HashCash stamps.
+"""
+
+__author__ = 'prussell'
+
+from hashlib import sha1
+from datetime import datetime
+from random import randint
+from math import ceil
+
+rand_chars = ([chr(x) for x in range(ord('a'), ord('z'))] +
+              [chr(x) for x in range(ord('A'), ord('Z'))] +
+              [chr(x) for x in range(ord('0'), ord('9'))] +
+              ['+', '-', '/'])
+
+
+char_map = {'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'}
+
+
+rc_len = len(rand_chars)
+
+min_bits = 0
+# Max number of bits for SHA-1 stamps
+max_bits = 160
+default_bits = 15
+
+def is_valid(stamp : str) -> bool:
+    return validate(int(stamp.split(':')[1]), stamp)
+
+def validate(nbits : int, stamp : str, encoding : str ='utf-8') -> bool:
+    if nbits < min_bits or nbits > max_bits:
+        raise ValueError("Param 'nbits' must be in range [0, 160), but is {}".format(nbits))
+
+    i = 0
+    total = 0
+    N = int(nbits/8)
+    hashed = sha1(stamp.encode(encoding)).digest()
+
+    while i < N:
+        total |= hashed[i]
+        i += 1
+
+    remainder = nbits % 8
+    if remainder != 0:
+        total |= hashed[i] >> (8 - remainder)
+
+    return total == 0
+
+def generate(nbits : int, resource : str, encoding : str ='utf-8') -> str:
+    # ver:bits:date:resource:[ext]:rand:counter
+    ver = 1
+    bits = nbits
+    date_str = datetime.utcnow().strftime("%Y%m%d%H%M%S")
+    ext = ''
+    rand = ''.join(rand_chars[randint(0, rc_len-1)] for x in range(0, 10))
+    counter = 0
+
+    result = None
+    while result is None:
+        #stamp = ":".join(str(elem) for elem in [ver, bits, date_str, resource, ext, rand, counter])
+        stamp = "{}{}".format(resource,counter)
+
+        if validate(nbits, stamp, encoding=encoding):
+            result = stamp
+            break
+
+        counter += 1
+
+    return result
+
+
+if __name__ == "__main__":
+
+    from argparse import ArgumentParser
+    parser = ArgumentParser()
+
+    parser.add_argument("NBITS", type=int, default=default_bits, help="Number of leading zeroes in a stamp", choices=range(max_bits+1))
+    parser.add_argument("RESOURCE", help="The resource string to use in the stamp. Ex: email address, ip address, etc")
+    parser.add_argument('-v', '--validate', action='store_true', help="Validate RESOURCE as a HashCash stamp")
+
+    args = parser.parse_args()
+
+    func = generate
+
+    if args.validate:
+        func = validate
+
+    print(func(args.NBITS, args.RESOURCE))