The software-efficient stream cipher HC-256 was proposed by Wu at FSE 2004. Due to its impressive performance, the cipher was also a well-received entrant to the ECRYPT eSTREAM competition. The closely related stream cipher HC-128, also designed by Wu, went on to find a place in the final portfolio of the eSTREAM contest. The cipher HC-256 is word-oriented, with 32 bits in each word, and uses a...

The stream cipher Py, which was designed by Biham and Seberry, is a submission for ECRYPT stream cipher competition. The cipher which is based on two large arrays (one is 256 bytes and the other is 1040 bytes) is specifically designed for high speed software applications (Py is more than 2.5 times faster than the RC4 on Pentium III). The paper, for the first time, detects a weakness in the mech...

In this paper, we investigate the security of SNOW-V, demonstrating two guess-and-determine (GnD) attacks against full version with complexities 2384 and 2378, respectively, one distinguishing attack a reduced variant complexity 2303. Our GnD use enumeration recursion to explore valid guessing paths, try truncate as many invalid paths possible at early stages by carefully designing order guessi...

Automated search methods based on Satisfiability Modulo Theory (SMT) problems are being widely used to evaluate the security of block ciphers against distinguishing attacks. While these provide a systematic and generic methodology, most their software implementations limited small set attacks, extending requires significant effort expertise. In this work, authors present cryptographic algorithm...

Kim et al. [4] and Contini et al. [3] studied on the security of HMAC and NMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. Especially, they considered the distinguishing attacks. However, they did not describe generic distinguishing attacks on NMAC and HMAC. In this paper, we describe the generic distinguishers to distinguish NMAC and HMAC with the birthday attack complexity and we prove the sec...

Stream ciphers are cryptographic primitives that are used to ensure the privacy of a message that is sent over a digital communication channel. In this thesis we will present new cryptanalytic results for several stream ciphers. The thesis provides a general introduction to cryptology, explains the basic concepts, gives an overview of various cryptographic primitives and discusses a number of d...

Our contributions are applying distinguishing attack on Linearly Filtered NLFSR as a primitive or associated with filter generators. We extend the attack on linear combinations of Linearly Filtered NLFSRs as well. Generally, these structures can be examined by the proposed techniques and the criteria will be achieved to design secure primitive. The attacks allow attacker to mount linear attack ...