This repository holds an implementation of a DoubleDES cipher along with a Meet In The Middle attack against that cipher. The attack and cipher are implemented in Java using the Java Cryptography Extension.

Read more about meet in the middle attacks here: https://en.wikipedia.org/wiki/Meet-in-the-middle_attack

Description of this repository files:

• DoubleDES.java: this file holds a class DoubleDES which allows one to take a pair of secret keys concatenated in a string along with a plaintext and returns the corresponding ciphertext encoded by a DoubleDES cipher.

• DoubleDESDecrypt.java: this file holds a class DoubleDESDecrypt which uses the same cipher in a decryption mode to take a ciphertext and along the two keys required and outputs the corresponding plaintext

• MITM.java: this file performs an attack against the cipher included in the above files. It does so by performing a meet in the middle attack. To simplify the computations, part of the two keys are provided as an input to the attack method.

First, here is how to encode a message. Suppose you want to encode 0123456789ABCDEF using keys 00000000000000 and 11111111111111, you run the following:

java DoubleDES 0000000000000011111111111111 0123456789ABCDEF

which should return the ciphertext 3057b90bd52bae5e1dc92a4ef6dd9775. Now, to decode you replace DoubleDES by DoubleDESDecrypt to get back 0123456789ABCDEF.

To run the meet in the middle attack, simply run MITM as the pair of plaintext and cipher text are hardcoded in the code, along with the partial keys to help with the run time.

If you have any questions or suggestions, feel free to submit pull requests or contact me using:

• Twitter: http://www.twitter.com/nicolaspapernot
• My Webpage: http://www.papernot.fr