def breakxor(raw, keysize=-1):
if(keysize == -1):
distances = get_probable_key_sizes(raw)
else:
diff = get_normalized_distance(raw, keysize, 4)
distances = [Distance(keysize, diff)]
best_decrypted = None
best_score = None
for dist in distances:
keysize = dist.keysize
blocks = [[] for _ in range(keysize)]
for i in range(0, len(raw)):
pos = i % keysize
blocks[pos].append(raw[i])
key = bytearray()
for block in blocks:
b, output, score = solve_xor_block(block)
key.append(b)
decrypted = xor_repeating(raw, key)
score = frequency.scoreof(decrypted)
if( best_score is None or score < best_score):
best_decrypted = (key, decrypted)
best_score = score
return best_decrypted
def solve_xor_block(encoded_bytes):
current_score = 0
current_byte = None
current_bytes = None
for b in range(0, 256):
test_byte = bytes([b])[0]
decoded_bytes = xor_against_byte(encoded_bytes, test_byte)
score = frequency.scoreof(decoded_bytes)
if current_score == 0 or score < current_score:
current_score = score
current_byte = test_byte
current_bytes = decoded_bytes
return (current_byte, current_bytes, current_score)
