International Association for Cryptologic Research

International Association
for Cryptologic Research


Martin Boesgaard


The Rabbit Stream Cipher - Design and Security Analysis
The stream cipher Rabbit was rst presented at FSE 2003 [6]. In the paper at hand, a full security analysis of Rabbit is given, focusing on algebraic attacks, approximations and di erential analysis. We determine the algebraic normal form of the main nonlinear parts of the cipher as part of a comprehensive algebraic analysis. In addition, both linear and nonlinear approximations of the next-state function are presented, as well as a differential analysis of the IV-setup function. None of the investigations have revealed any exploitable weaknesses. Rabbit is characterized by high performance in software with a measured encryption/decryption speed of 3.7 clock cycles per byte on a Pentium III processor.
Badger - A Fast and Provably Secure MAC
We present Badger, a new fast and provably secure MAC based on universal hashing. In the construction, a modified tree hash that is more efficient than standard tree hash is used and its security is being proven. Furthermore, in order to derive the core hash function of the tree, we use a novel technique for reducing $\Delta$-universal function families to universal families. The resulting MAC is very efficient on standard platforms both for short and long messages. As an example, for a $64$-bit tag, it achieves performances up to 2.2 and 1.2 clock cycles per byte on a Pentium III and Pentium 4 processor, respectively. The forgery probability is at most $2^{-52.2}$.