87 lines
2.0 KiB
Python
87 lines
2.0 KiB
Python
#!/usr/bin/env python
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"""
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Module to generate and validate HashCash stamps.
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"""
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__author__ = 'prussell'
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from hashlib import sha1
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from datetime import datetime
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from random import randint
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from math import ceil
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rand_chars = ([chr(x) for x in range(ord('a'), ord('z'))] +
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[chr(x) for x in range(ord('A'), ord('Z'))] +
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[chr(x) for x in range(ord('0'), ord('9'))] +
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['+', '-', '/'])
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char_map = {'0': '0000',
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'1': '0001',
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'2': '0010',
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'3': '0011',
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'4': '0100',
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'5': '0101',
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'6': '0110',
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'7': '0111',
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'8': '1000',
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'9': '1001',
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'a': '1010',
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'b': '1011',
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'c': '1100',
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'd': '1101',
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'e': '1110',
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'f': '1111'}
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rc_len = len(rand_chars)
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min_bits = 0
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# Max number of bits for SHA-1 stamps
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max_bits = 160
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default_bits = 15
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def is_valid(stamp: str) -> bool:
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return validate(int(stamp.split(':')[1]), stamp)
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def validate(nbits: int, stamp: str, encoding: str = 'utf-8') -> bool:
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if nbits < min_bits or nbits > max_bits:
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raise ValueError("Param 'nbits' must be in range [0, 160), but is {}".format(nbits))
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i = 0
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total = 0
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N = int(nbits / 8)
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hashed = sha1(stamp.encode(encoding)).digest()
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while i < N:
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total |= hashed[i]
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i += 1
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remainder = nbits % 8
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if remainder != 0:
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total |= hashed[i] >> (8 - remainder)
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return total == 0
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def generate(nbits: int, resource: str, encoding: str = 'utf-8') -> str:
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# ver:bits:date:resource:[ext]:rand:counter
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ver = 1
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bits = nbits
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date_str = datetime.utcnow().strftime("%Y%m%d%H%M%S")
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ext = ''
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rand = ''.join(rand_chars[randint(0, rc_len - 1)] for x in range(0, 10))
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counter = 0
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result = None
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while result is None:
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stamp = "{}{}".format(resource, counter)
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if validate(nbits, stamp, encoding=encoding):
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result = stamp
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break
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counter += 1
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return result
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