Enes Pašalić: Fast encryption schemes - from classical to contemporary design

Symmetric-key cryptography is a cryptographic primitive that uses the same secret key for both encryption and decryption. Both the encryption and decryption is of magnitude 1000 times faster compared to public key cryptosystems, making this method preferable whenever the encryption of relatively large messages is required. The symmetric key encryption schemes are traditionally divided into two major families, so called block ciphers and stream ciphers. The famous Data Encryption Standard (DES), that is probably a most prominent and important block cipher encryption algorithm, was replaced by a new standard Advanced Encryption Standard in October 2000. In case of stream cipher encryption schemes, there is no standard algorithm and the process of adopting a standard for this cryptographic primitive is ongoing. EStream project is an open call for stream cipher proposals, and the final objective is to select one or two candidates for two dedicated purposes: fast software encryption and low hardware cost encryption. The major advantage of stream ciphers over block ciphers is either its exceptional encryption speed (they are several times faster than block ciphers) or the possibility of designing an encryption device for restricted hardware environments. For the latter application, encryption using stream cipher is actually the only alternative of choice. One such application is Radio-frequency Identifier (RFID) which is an automatic identication method, relying on storing and remotely retrieving data using devices called RFID tags. This seminar addresses some frequently used design rationales for stream cipher algorithms. The goal is to demonstrate that exceptionally simple design methods still may result in both secure and fast encryption algorithms.