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Diffstat (limited to 'Assignment 3/2des-demo.py')
| -rwxr-xr-x | Assignment 3/2des-demo.py | 74 |
1 files changed, 0 insertions, 74 deletions
diff --git a/Assignment 3/2des-demo.py b/Assignment 3/2des-demo.py deleted file mode 100755 index b5b7247..0000000 --- a/Assignment 3/2des-demo.py +++ /dev/null @@ -1,74 +0,0 @@ -#!/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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