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Diffstat (limited to 'Assignment 3/break.py')
| -rwxr-xr-x | Assignment 3/break.py | 141 |
1 files changed, 0 insertions, 141 deletions
diff --git a/Assignment 3/break.py b/Assignment 3/break.py deleted file mode 100755 index 7666d33..0000000 --- a/Assignment 3/break.py +++ /dev/null @@ -1,141 +0,0 @@ -#!/usr/bin/python -import sys, getopt, binascii, random, time, os.path, time -from Crypto.Cipher import DES - -dictionary = {} - -# 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 - -# Create a dictionary for the first 2^l keys and a given plaintext -def createDictionary(plaintext, l): - for n in range(0, pow(2, l)): - encryption = DES.new(nthKey(n), DES.MODE_ECB).encrypt(plaintext) - if encryption in dictionary: - dictionary[encryption].append(n) - else: - dictionary[encryption] = [n] - -# Read the dictionary from a file if it exists, or generate it -def readOrMakeDictionary(plaintext, l): - if os.path.isfile('dict-' + binascii.b2a_hex(plaintext) + '-' + str(l) + '.txt'): - with open('dict-' + binascii.b2a_hex(plaintext) + '-' + str(l) + '.txt') as f: - for line in f: - dictionary[binascii.a2b_hex(line[:16])] = [int(x) for x in line[17:-1].split(',')] - return False - else: - createDictionary(plaintext, l) - return True - -# Save the dictionary to a file -def saveDictionary(plaintext, l): - dictionary_file = open('dict-' + binascii.b2a_hex(plaintext) + '-' + str(l) + '.txt', 'w') - for encryption in dictionary: - dictionary_file.write(binascii.b2a_hex(encryption) + ':' + ','.join(str(x) for x in dictionary[encryption]) + '\n') - print 'Saved dictionary as dict-' + binascii.b2a_hex(plaintext) + '-' + str(l) + '.txt' - -def main(argv): - l = 24 - plaintext = '' - ciphertext = '' - save_dictionary = False - - # Parse arguments. Use -h for help. - try: - opts, args = getopt.getopt(argv, "hl:p:c:s") - except getopt.GetoptError: - usage() - sys.exit(2) - - for opt, arg in opts: - if opt == '-h': - usage() - sys.exit() - elif opt == '-l': - l = int(arg) - elif opt == '-p': - plaintext = binascii.a2b_hex(arg) - elif opt == '-c': - ciphertext = binascii.a2b_hex(arg) - elif opt == '-s': - save_dictionary = True - - assert plaintext != '' - assert ciphertext != '' - - # Make the dictionary if it doesn't exist yet - print 'Making dictionary (p:' + binascii.b2a_hex(plaintext) + ';l:' + str(l) + ')...', - timer = time.clock() - if not readOrMakeDictionary(plaintext, l): - save_dictionary = False - print str(time.clock() - timer) + 's' - - if save_dictionary: - saveDictionary(plaintext, l) - - # Find matches - print 'Finding matches...', - timer = time.clock() - time_key = time_decryption = time_matching = 0 - matches = [] - for k in range(0, pow(2,l)): - # Generate key - time_t = time.clock() - key = nthKey(k) - time_key += time.clock() - time_t - - # Decrypt - time_t = time.clock() - des = DES.new(key, DES.MODE_ECB) - decryption = des.decrypt(ciphertext) - time_decryption += time.clock() - time_t - - # Find matches - time_t = time.clock() - if decryption in dictionary: - [matches.append({'k1': nthKey(i), 'k2': key}) for i in dictionary[decryption]] - time_matching += time.clock() - time_t - print str(time.clock() - timer) + 's' - - print 'Key generation: ' + str(time_key) + 's' - print 'Decryption: ' + str(time_decryption) + 's' - print 'Matching dictionary: ' + str(time_matching) + 's' - - for match in matches: - print 'k1: ' + binascii.b2a_hex(match['k1']) + '; k2: ' + binascii.b2a_hex(match['k2']) - -def usage(): - print 'Usage: break.py -p <plaintext> -c <ciphertext> [-l <keylength>] [-s]' - print ' plaintext : plaintext of the known-plaintext attack' - print ' ciphertext : ciphertext of the known-plaintext attack' - print ' keylength : pick keys from the first 2^l keys (default: 24)' - print ' -s : save the dictionary for this plaintext and keylength to a file' - -if __name__ == "__main__": - main(sys.argv[1:])
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