Xortool is a python tool that allows you to analyze multi-byte xor cipher and guess the xor key (based on count of equal chars) and the key length (base on knowledge of most frequent char).
Note: Python3 is not supported, use python 2.x.
Usage:
xortool [-h|--help] [OPTIONS] [<filename>]
Options:
-l,--key-length length of the key (integer)
-c,--char most possible char (one char or hex code)
-m,--max-keylen=32 maximum key length to probe (integer)
-x,--hex input is hex-encoded str
-b,--brute-chars brute-force all possible characters
-o,--brute-printable same as -b but will only use printable
The most common use is to pass just the encrypted file and the most frequent character (usually 00 for binaries and 20 for text files) - length will be automatically chosen:
tests $ xortool tool_xored -c 20
The most probable key lengths:
2: 5.6%
5: 7.8%
8: 6.0%
10: 11.7%
12: 5.6%
15: 7.6%
20: 19.8%
25: 7.8%
28: 5.7%
30: 11.4%
Key-length can be 5*n
1 possible key(s) of length 20:
an0ther s3cret \xdd key
Here, the key is longer than default 32 limit:
tests $ xortool ls_xored -c 00 -m 64
The most probable key lengths:
3: 3.3%
6: 3.3%
9: 3.3%
11: 7.0%
22: 6.9%
24: 3.3%
27: 3.2%
33: 18.4%
44: 6.8%
55: 6.7%
Key-length can be 3*n
1 possible key(s) of length 33:
really long s3cr3t k3y... PADDING
So, if automated decryption fails, you can calibrate:
(-m) max length to try longer keys.
(-l) selected length to see some interesting keys.
(-c) the most frequent char to produce right plaintext.
