| 0,0 → 1,66 |
|---|
| import math |
| |
| substitution_map = {14:0,4:1,13:2,1:3,2:4,15:5,11:6,8:7,3:8,10:9,6:10,12:11,5:12,9:13,0:14,7:15} |
| |
| key = [3,10,9,4,13,6,3,15] # Key |
| key_length = len(key) * 4 # Calculate length of the key in bits |
| bytes_per_key = key_length / 8 # Calculate the number of bytes for each round key (4 for a 32-bit key) |
| rounds = int(math.log(key_length,2)) # Calculate the number of rounds (5 for a 32-bit key) |
| |
| ciphertext = [6,4,15,13] |
| |
| def get_key(key, round): |
| '''Returns the round key for the specified key. |
| The round key is bytes_per_key bytes starting at the specified offset determined by round.''' |
| round -= 1 |
| ret = [] |
| for index in range(bytes_per_key): |
| ret.append(key[index + round]) |
| return ret |
| |
| def xor_array(array, key): |
| '''Xor the two arrays and returns the result.''' |
| ret = [] |
| for index in range(len(array)): |
| ret.append(array[index] ^ key[index]) |
| return ret |
| |
| def sub_array(array): |
| '''Runs the given array through the substitution map and returns the result.''' |
| ret = [] |
| for index in range(len(array)): |
| ret.append(substitution_map[array[index]]) |
| return ret |
| |
| def perm_array(array): |
| '''Permutes the given array and returns the results.''' |
| ret = [] |
| for index in range(bytes_per_key-1,-1,-1): |
| value = 0 |
| for entry in array: |
| value <<= 1 |
| value |= (entry >> index) & 1 |
| ret.append(value) |
| return ret |
| |
| if __name__ == '__main__': |
| working_array = ciphertext # Initial array is the ciphertext |
| print "Ciphertext:\t\t\t\t", ciphertext |
| print |
| |
| # Print out the results for each step as it is calculated |
| for round in range(rounds,1,-1): |
| print "Round {0} Key:\t\t\t".format(round), get_key(key, round) |
| working_array = xor_array(working_array, get_key(key, round)) |
| print "Round {0} U (xor'ed):\t\t".format(round),working_array |
| if round != rounds: |
| working_array = perm_array(working_array) |
| print "Round {0} W (perm'ed):\t".format(round),working_array |
| working_array = sub_array(working_array) |
| print "Round {0} V (sub'ed):\t\t".format(round),working_array |
| print |
| |
| # Print out the final round key and xor'ed result (plaintext) |
| print "Round 1 Key:\t\t\t",get_key(key, 1) |
| working_array = xor_array(working_array, get_key(key, 1)) |
| print("Plaintext (xor'ed):\t\t"), working_array |