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TWEET # Untitled a guest Oct 18th, 2019 66 Never
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1. def extend_round_key(cipher_matrix, rounds):
2.     rcon = [['01','00','00','00'],
3.         ['02','00','00','00'],
4.         ['04','00','00','00'],
5.         ['08','00','00','00'],
6.         ['10','00','00','00'],
7.         ['20','00','00','00'],
8.         ['40','00','00','00'],
9.         ['80','00','00','00'],
10.         ['1B','00','00','00'],
11.         ['36','00','00','00']]
12.     extended_round_key = cipher_matrix.copy() # copy the provided key to extend
13.     for extension in range(rounds): # perform an extension for each round
14.         for j in range(len(extended_round_key)): # do this four times
15.             for i in range(len(extended_round_key)): # do this four times
16.                 if (len(extended_round_key[i]) % 4 == 0): # if the new position is evenly divisible by 4 do the complicated thing
17.                     extended_round_key[i] += [bin_to_hex(xor(xor((''.join(byte_substitution(hex_to_bin(extended_round_key[(i+1)%len(extended_round_key)][len(extended_round_key[i])-1])))),hex_to_bin(extended_round_key[i][-4])),hex_to_bin(rcon[extension][i])))]
18.                 else: # otherwise do the simple thing
19.                     extended_round_key[i] += [bin_to_hex(xor(hex_to_bin(extended_round_key[i][-1]), hex_to_bin(extended_round_key[i][-4])))]
20.     return extended_round_key # return the extended key
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