with open("test_known.txt") as f:
    with open("test.txt", 'rb') as e:
        i,j = 0,0
        e.seek(28)
        output = ""
        pad = [0,0,0,0,0,0,0,0]
        for char in f.read():
            if j == 0:
                char2 = e.read(1)
                pad[i] = ord(char) ^ ord(char2)
                output += chr(pad[i] ^ ord(char2))
            else:
                output += chr(pad[i] ^ ord(e.read(1)))
            i += 1
            if i % 8 == 0:
                i = 0
                j = (j + 1) % 8
print output