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#!/usr/bin/python
import sys, getopt, binascii, random
from Crypto.Cipher import DES
# From http://stackoverflow.com/a/843846/1544337
# 1 for odd parity, 0 for even parity
# Was used only in a previous version of nthByte
# def parity(b):
# c = 0
# while b != 0:
# c += 1
# b &= b - 1
# return c % 2
# Find the nth possibility for a byte with odd parity
oddBytes = [1,2,4,7,8,11,13,14,16,19,21,22,25,26,28,31,32,35,37,38,41,42,44,47,49,50,52,55,56,59,61,62,64,67,69,70,73,74,76,79,81,82,84,87,88,91,93,94,97,98,100,103,104,107,109,110,112,115,117,118,121,122,124,127,128,131,133,134,137,138,140,143,145,146,148,151,152,155,157,158,161,162,164,167,168,171,173,174,176,179,181,182,185,186,188,191,193,194,196,199,200,203,205,206,208,211,213,214,217,218,220,223,224,227,229,230,233,234,236,239,241,242,244,247,248,251,253,254]
def nthByte(n):
return oddBytes[n]
# c = -1 # This is the old version. The new version uses a faster lookup table.
# b = 0
# while c != n:
# b += 1
# if parity(b) == 1:
# c += 1
# return b
# Find the nth key in which all bytes have odd parity
def nthKey(n):
key = ''
for b in range(7,-1,-1):
key += chr(nthByte((n >> b*7) & 0x7f))
return key
def main(argv):
l = 24
# Parse arguments. Use -h for help.
try:
opts, args = getopt.getopt(argv, "hl:")
except getopt.GetoptError:
usage()
sys.exit(2)
for opt, arg in opts:
if opt == '-h':
usage()
sys.exit()
elif opt == '-l':
l = int(arg)
# generate two keys
r = random.SystemRandom()
k1 = nthKey(r.randint(0, pow(2, l) - 1))
k2 = nthKey(r.randint(0, pow(2, l) - 1))
print 'k_1: %s' % binascii.b2a_hex(k1)
print 'k_2: %s' % binascii.b2a_hex(k2)
round1 = DES.new(k1, DES.MODE_ECB)
round2 = DES.new(k2, DES.MODE_ECB)
# Some random plaintext - ciphertext pairs to verify the working of this code
print 'plaintext : ciphertext'
for n in range(0,10):
pt = '{:016x}'.format(r.randint(0, pow(2, 64) -1))
ct = round2.encrypt(round1.encrypt(binascii.a2b_hex(pt)))
print pt + ' : ' + binascii.b2a_hex(ct)
def usage():
print 'Usage: 2des-demo.py [-l <keylength>]'
print ' keylength : pick keys from the first 2^l keys (default: 24)'
if __name__ == "__main__":
main(sys.argv[1:])
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