Automated techniques for the cryptanalysis and design of symmetric-key ciphers and protocols.

Cryptography is the study of mathematical techniques that ensure the confidentiality and integrity of information. This relatively new field started out as classified military technology, but has now become commonplace in our daily lives. Cryptography is not only used in banking cards, secure websites and electronic signatures, but also in public transport cards, car keys and garage door openers. Two building blocks in the domain of symmetric-key cryptography are block ciphers and hash functions. Block ciphers use a secret key to transform a plaintext into a cipher- text, in such a way that this secret key is needed to recover the original plaintext. Hash functions transform an arbitrary-length message into a fixed-length hash value. These hash values can serve as “fingerprints” for the original messages: it should be infeasible to find two distinct messages with the same hash value (a collision). The research will focus on automated techniques which can be used to analyze a wide variety of symmetric-key algorithms. Recently, many novel techniques have been developed, such as rebound cryptanalysis, biclique attacks and rotational cryptanalysis. By developing broadly applicable automated techniques for cryptanalysis, we can integrate these novel techniques into a new framework. We will investigate how we can use our results to improve the security and/or efficiency of protocols, such as lightweight cryptographic protocols that can be used for RFID tags and sensor networks.