The Rebound Attack and Subspace Distinguishers: Application to Whirlpool

We introduce the rebound attack as a variant of differential cryptanalysis on hash functions and apply it to the hash function Whirlpool, standardized by ISO/IEC. We give attacks on reduced variants of the Whirlpool hash function and the Whirlpool compression function. Next, we introduce the subspace problems as generalizations of near-collision resistance. Finally, we present distinguishers based on the rebound attack, that apply to the full compression function of Whirlpool and the underlying block cipher $W$

KISS: A Bit Too Simple

KISS (`Keep it Simple Stupid\u27) is an efficient pseudo-random number generator specified by G. Marsaglia and A. Zaman in 1993. G. Marsaglia in 1998 posted a C version to various USENET newsgroups, including \texttt{sci.crypt}. Marsaglia himself has never claimed cryptographic security for the KISS generator, but many others have made the intellectual leap and claimed that it is of cryptographic quality. In this paper we show a number of reasons why the generator does not meet the KISS authors\u27 claims, why it is not suitable for use as a stream cipher, and that it is not cryptographically secure. Our best attack requires about 70 words of generated output and a few hours of computation to recover the initial state

Complexity measures for classes of sequences and cryptographic apllications

Pseudo-random sequences are a crucial component of cryptography, particularly in stream cipher design. In this thesis we will investigate several measures of randomness for certain classes of finitely generated sequences. We will present a heuristic algorithm for calculating the k-error linear complexity of a general sequence, of either finite or infinite length, and results on the closeness of the approximation generated. We will present an linear time algorithm for determining the linear complexity of a sequence whose characteristic polynomial is a power of an irreducible element, again presenting variations for both finite and infinite sequences. This algorithm allows the linear complexity of such sequences to be determined faster than was previously possible. Finally we investigate the stability of m-sequences, in terms of both k-error linear complexity and k-error period. We show that such sequences are inherently stable, but show that some are more stable than others

Preserving the confidentiality of digital images using a chaotic encryption scheme

Confidentiality of digital images is an important requirement for many multimedia applications and services. To maintain confidentiality, encryption of digital images is essential. Digital images are usually very large and encrypting such bulky data induces many performance overheads, which can be too expensive for real-time applications in resource constrained environments. In this paper, we propose a chaotic image encryption scheme which satisfies the need for both light-weightedness and security. To justify the security and efficiency, the new cipher was evaluated using a series of statistical tests. These tests included a visual testing and a histogram analysis, a randomness analysis, a correlation analysis, an entropy analysis and an image encryption quality analysis. Based on all analyses and experimental results, it is concluded that the proposed scheme is effective, efficient and trustworthy and therefore can be adopted for image encryption