Ccrypt
A python library implementation of some classical cipher primitives and cryptanalysis functions.
Current ccrypt only works on GNU Linux systems.
SYNOPSIS
To access all functions availble in the library, simply import them all by wildcard.
from ccrypt import *What's it good for?
This project might be useful for CTFs using simple transposition and substitution ciphers.
Examples
Discover partial key in a repeating XOR cipher:
>>> from ccrypt import *
>>> c = xor_repeat("This is a simple test message", "TEST")
>>> c
"\x00-:'t, t5e =95?1t16' e>1'6231"
>>> discover_pt(c, "simple", xor_repeat)
['sDWW\x18I', '^SJ\x04@E', 'IN\x19\\L\x11', 'T\x1dAP\x18P', '\x07EM\x04Y\x00', '_I\x19E\tE', 'S\x1dX\x15LX', '\x07\\\x08PQ\\', 'F\x0cMMUP', '\x16IPIYZ', 'STTEST', 'NPXO]\x11', 'J\\RA\x18T', 'FV\\\x04]S', 'LX\x19AZB', 'B\x1d\\FKE', '\x07X[WL\x00', 'B_JP\t[', 'ENM\x15RT', 'TI\x08N]B', 'S\x0cSAKS', '\x16W\\WZW', 'MXJF^V', 'BN[B_T', 'T__C]', 'E[^A', 'AZ\\', '@X', 'B']
>>>Use monoalphabetic or repeating XOR ciphers.
>>> xor_repeat("This is kind of cool", "SEC")
"\x07-* e* e(:+'s*%s&,<)"
>>> xor_repeat(xor_repeat("This is kind of cool", "SEC"), "SEC")
'This is kind of cool'
>>> xor_c("Only a single character for this one", "F")
"\t(*?f'f5/(!*#f%.'4'%2#4f )4f2./5f)(#"
>>>Use a polyalphabetic transposition cipher:
>>> poly_shift("Just shifting about.", "KEY")
'\x95\xba\xcc\xbfe\xcc\xb3\xae\xbf\xbf\xae\xc7\xb2e\xba\xad\xb4\xce\xbfs'
>>> poly_unshift(poly_shift("Just shifting about.", "KEY"), "KEY")
'Just shifting about.'
>>>Brute force a XOR repeating cipher:
>>> c = xor_repeat("Just a simple plaintext message", "KEY")
>>> c
"\x010*?e8k60&55.e)'$0%1<31y& *8$>."
>>> brute_xor_repeat(c, 3, just_text, just_text)
Just a simple plaintext message
[('KEY', 'Just a simple plaintext message')]Find candidate polyalphabetic transpositional keys:
>>> c = poly_shift("What's the go?", "KEY")
>>> find_poly_keys(c, 3, just_text)
['KER', 'KES', 'KET', 'KEU', 'KEV', 'KEW', 'KEX', 'KEY', 'KE[', 'KEg', 'KEh', 'KEi', 'KEj', 'KEk', 'KEm', 'KEr', 'KEs', 'KEt', 'KEu', 'KEv', 'KEw', 'KEx', 'KEy', 'KE{']
>>>Use some simple fitness tests:
>>> is_english("What say you?")
True
>>> c = xor_repeat("Super secret message", "KEY")
>>> is_english(c)
False
>>> is_english("{}{J(*J_F#(_@HF")
False
>>>
>>> just_text("Just some text__")
True
>>> just_text("Just some text_()_#JF}_!(FHJ_")
False
>>>Easily determine decrypted content's file type:
>>> whatfile("\x7fELF\x02")
'ELF 64-bit'Find ngrams in ciphertext and plaintext:
>>> c = xor_repeat("Can you guess the key length here over this very long piece of text which should help you find a cooincidence of plain and key repetition.", "XYZ")
>>> find_ngrams(c, 3, 5)
[(('#', 'x', '5'), 2), ((',', '=', '+'), 2), (('3', '<', '#'), 2), (('z', '3', '<'), 2), (('<', '#', 'x'), 2)]
>>>Read ccrypt.py for a full list of functions.
LICENSE
The project and its content are licensed under GPLv3. No warranty is given for its use and the author takes no responsibilty for its misuse.