Partial Xor Key Bruteforcing

gistfile1.txt

cipher = []

def loadFile(file):
    with open(file) as f:
        lines = f.read().splitlines()
    return lines

def getLetter(pos, letter):
    char = cipher[pos]
    for x in xrange(0,255):
        if char^x == ord(letter):
            return x

def getPercentAscii(input):
    count = 0
    for char in input:
        if char.isalnum():
            count+=1
    return int(100 * float(count)/float(575))

def getKey(keyStr, pos):
    expected = list(keyStr)
    key = []
    for id,char in enumerate(expected):
        key.append(getLetter(pos+id, char))
    return key

def getCipherData(pos, length):
    newCipher = cipher[pos:]
    return newCipher[:length]

def isValid(word, key, output):
    if len(word)>4 and word in output and word != keyStr and word not in keyStr:
        return True
    return False

def xorAttempt(key, pos, lenGuess):
    out = []
    for x in xrange(len(cipher)/lenGuess):
        newPos = pos+(x*lenGuess)
        cipherData = getCipherData(newPos, lenGuess)
        for id,char in enumerate(cipherData):
            xorChar = chr(char^key[id%len(key)])
            if xorChar.isalnum():
                out.append(xorChar)
            else:
                out.append(".")
        out.append(" ")
    return "".join(out)

wordDict = loadFile('words.txt')
guessWords = ["cipher","encryption","case","detective"]

for keyStr in guessWords:

    percentThreshold = 50

    for keyLenGuess in xrange(20,30):
        for pos in xrange(len(cipher)-len(keyStr)):
            key = getKey(keyStr, pos)
            output = xorAttempt(key, pos, keyLenGuess)
            percent = getPercentAscii(output)
            if percent>percentThreshold:
                for word in wordDict:
                    if isValid(word, keyStr, output):
                        print "-"*20
                        print "Word guess: ", keyStr
                        print "Key Len guess: ", keyLenGuess
                        print "Position: ", pos
                        print "Key: ", key
                        print "Found: ", word
                        print "-"*20
                        print output
                        print "-"*20