Key Size Simplified

key_size_simplified.py

b = bytearray("".join(list(open("6.txt", "r"))).decode("base64"))

normalized_distances = []
for KEYSIZE in range(2, 40):
    b1 = b[:KEYSIZE]
    b2 = b[KEYSIZE:KEYSIZE*2]
    b3 = b[KEYSIZE*2:KEYSIZE*3]
    b4 = b[KEYSIZE*3:KEYSIZE*4]

    normalized_distance = float(
        hamming_distance(b1, b2) +
        hamming_distance(b2, b3) +
        hamming_distance(b3, b4)
    ) / (KEYSIZE * 3)

    normalized_distances.append(
        (KEYSIZE, normalized_distance)
    )
    
normalized_distances = sorted(normalized_distances, key=lambda (_, y): y)
# [(2, 2.0), (3, 2.6666666666666665), (29, 2.793103448275862), ...]