Showing papers on "Sponge function published in 2005"

A MAC Forgery Attack on SOBER-128 *

Abstract: SOBER-128 is a stream cipher designed by Rose and Hawkes in 2003. It can be also used for generating Message Authentication Codes (MACs) and an authenticated encryption. The developers claimed that it is diffcult to forge MACs generated by both functions of SOBER-128, though, the security assumption in the proposal paper is not realistic in some instances. In this paper, we examine the security of these message authentication mechanisms of SOBER-128 under security channel model. As a result, we show that both a MAC generation and an authenticated encryption are vulnerable against differential cryptanalysis. The success probabilities of the MAC forgery attack are estimated at 2-6 and 2-27 respectively. In addition, we show that some secret bits are revealed if a key is used many times.

Authenticated encryption and steganography in unconditional security setting

Abstract: We address authenticated encryption, the cryptographic technique that simultaneously provides both confidentiality and authenticity, and steganography that hides the very existence of messages. We focus on the security of these techniques against adversaries with unbounded computational resources. First, we reveal the strong security notion of unconditionally secure authenticated encryption and show how to achieve it. Second, we study unconditionally secure stegosystems under active attacks and show how to construct them by the above mentioned unconditionally secure authenticated encryption schemes

Non-Linearity and Security of Self Synchronizing Stream Ciphers

Abstract: Several proposed chaos based ciphers exploit the ergodic property of chaotic orbits. As chaotic systems are unstable and have sensitive dependence on initial conditions, the main difficulty for the receiver is to reproduce the chaotic signal that has been generated by the sender in order to correctly decrypt the message. This is performed by a self synchronizing device. In discrete cryptography, the closest scheme is the so called self synchronizing stream cipher (SSSC). After recalling general security models for assessing cryptographic algorithms, we present SSSC scheme and two examples of cryptanalysis. In order to resist to theses attacks, the ciphering function must satisfy high non-linearity properties which are presented.