def _crackRepeatingXOR(byteObject, frequentLetters, keySizeRange, blockNumber):
if not isBytes(byteObject):
raise ValueError("Input must be a bytes object")
keySizes = getLikelyKeySizes(byteObject,
keySizeRange,
blockNumber,
howMany=3)
bestGuess = Candidate(0, b'', b'', b'')
for keySize in keySizes:
blocks = divideIntoBlocks(byteObject, keySize)
possibleKey = bytearray()
for block in blocks:
candidate = _crackSingleXOR(block, frequentLetters)
# This key length can never be the correct key length
if candidate.key == b'':
break
possibleKey.append(candidate.key[0])
if len(possibleKey) != keySize:
continue
possibleKey = bytes(possibleKey)
secret = fixedXOR(byteObject,
repeatPerCharacter(possibleKey, len(byteObject)))
score = calculateScore(secret, frequentLetters)
if score > bestGuess.score and encodedByUTF8(secret):
bestGuess = Candidate(score, possibleKey, byteObject, secret)
return bestGuess
def _crackSingleXOR(byteObject, frequentLetters):
if not isBytes(byteObject):
raise ValueError("Input must be a bytes object")
bestCandidate = Candidate(0, b'', b'', b'')
# We skip 0, since XORing against a bunch of 0s isn't going to do anything
byteLength = len(byteObject)
for i in range(1, 256):
possibleKey = repeatPerCharacter(bytes([i]), byteLength)
secret = fixedXOR(byteObject, possibleKey)
score = calculateScore(secret, frequentLetters)
if score > bestCandidate.score and encodedByUTF8(secret):
bestCandidate = Candidate(score, possibleKey, byteObject, secret)
return bestCandidate
def crackXOR(byteObject, scoreFile, EType):
if not isBytes(byteObject):
byteObject = hex2bytes(byteObject) if isHex(
byteObject) else byteObject.encode()
frequentLetters = {
key.encode(): value
for key, value in readJSON(scoreFile).items()
}
if EType == XORType.SINGLE:
return _crackSingleXOR(byteObject, frequentLetters)
elif EType == XORType.REPEATING:
return _crackRepeatingXOR(byteObject,
frequentLetters,
keySizeRange=(2, 40),
blockNumber=4)
else:
raise NotImplementedError
def test_3_check_bytes_with_invalid_bytes(self):
b = 'deadbeef'
assert not isBytes(bytes)
def test_2_check_bytes_with_valid_bytes(self):
b = bytes.fromhex('deadbeef')
assert isBytes(b)