Cryptosystem Design and Cryptanalysis

The specific scope for the topics below can be adjusted for either Bachelor or Master Students.

  • Single-Page Cryptography

You have been captured and wrongly imprisoned and need to communicate an encrypted message to your outside contact with an emergency key phrase that you both memorized in case of danger. Luckily, in your thesis you designed a cryptographic system that fits only on one regular page which is easy enough to memorize. Since you can only send one message, you want to make sure that you have memorized the "implementation" correctly. That's why you also memorized an easy self testing procedure, with which you can test if your implementation is correct. Now that everything is correct, you can use your Mini-Encryption System to encrypt the message so that it is only readable by your contact in the outside world which knows the key phrase.

An example for such a system could be the RC4 stream cipher. Unfortunately, RC4's security has been semi-successfully attacked before and it provides neither a way to encrypt multiple messages under the same key nor does it provide authentication.

  • Easy Attacks - Attacking the AEZ Cryptosystem

AEZ (pronounced "easy") is a cryptosystem, which uses four rounds of the AES as the internal building block. The goal is to describe attacks, when this building block is reduced to less than four rounds.

  • Leakage-Resilient Symmetric Cryptosystems

In cryptography, "leakage resilience" is the ability of a cryptosystem to provide security even when the adversary has access to a side-channel, such as, e.g., a power consumption trail from operations using the secret key. The goal is to study symmetric cryptosystems, which have been claimed to be "leakage-resilient" by their designers.