CTF-Katana

John Hammond | February 1st, 2018

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This repository, at the time of writing, will just host a listing of tools and commands that may help with CTF challenges. I hope to keep it as a "live document," and ideally it will not die out like the old "tools" page I had made (https://github.com/USCGA/tools).

Hopefully, at some point I will develop software that will run through a lot of the low-hanging fruit and simple command-line tools, generate a report and have all the output in one place.

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Steganography

• steghide

  A command-line tool typically used alongside a password or key, that could be uncovered some other way when solving a challenge.

• [zsteg][zsteg]

• Morse Code

  Always test for this if you are seeing two distinct values... it may not always be binary!

• Whitespace

  Tabs and spaces could be representing 1's and 0's and treating them as a binary message... or, they could be whitespace done with snow or

• snow

  A tool for whitespace steganography (see above)

Cryptography

• XOR

  ANY text could be XOR'd. Techniques for this are Trey's code, and XORing the data against the known flag format.

• Caesar Cipher

  https://www.dcode.fr/caesar-cipher

• Vigenere Cipher

• Beaufourt Cipher

  https://www.dcode.fr/beaufort-cipher

• Transposition Cipher

• RSA: Classic RSA

• RSA: Multi-prime RSA

• RSA: Weiner's Little D Attack

  The telltale sign for this kind of challenge is an enormously large e value. Typically e is either 65537 (0x10001) or 3 (like for a Chinese Remainder Theorem challenge)

• RSA: Chinese Remainder Attack

  These challenges can be spotted when given mutiple c cipher texts and multiple n moduli. e must be the same number of given c and n pairs.

• Elgamal

• Affine Cipher

• Substitution Cipher

  https://quipqiup.com/

• Railfence Cipher

  http://rumkin.com/tools/cipher/railfence.php

• Playfair Cipher

  https://en.wikipedia.org/wiki/Playfair_cipher

• Polybius Square

  https://www.braingle.com/brainteasers/codes/polybius.php

• The Engima

  http://enigma.louisedade.co.uk/enigma.html, https://www.dcode.fr/enigma-machine-cipher

• AES ECB

  The "blind SQL" of cryptography... leak the flag out by testing for characters just one byte away from the block length.