def break_repeating_key_xor(ct, key_size):
blocks = [ct[i:i+key_size] for i in range(0, len(ct), key_size)]
# "make a block that is the first byte of every block, and a block that
# is the second byte of every block, and so on."
transported_blocks = list(itertools.zip_longest(*blocks, fillvalue=0))
# Each block in transported_blocks was encrypted with the same byte
# So we can just use the code that breaks single byte XOR from challenge 3
key = [c3.bruteforce(bytes(tb))[0] for tb in transported_blocks]
return bytes(key)
def find_single_byte_xor(lines):
most_likely_decryption_of_lines=[(i,c3.bruteforce(l)[2]) for i,l in lines]
def score(t):
return c3.freq_score(t[1])
return max(most_likely_decryption_of_lines, key=score)
