Improved Linear Consistency Attack on Irregular Clocked Keystream Generators
نویسنده
چکیده
In this paper we propose a new attack on a general model for irregular clocked keystream generators. The model consists of two feedback shift registers of lengths l1 and l2, where the first shift register produces a clock control sequence for the second. This model can be used to describe among others the shrinking generator, the step-1/step2 generator and the stop and go generator. We prove that the maximum complexity for attacking such a model is only O(21 ).
منابع مشابه
An Improved Correlation Attack Against Irregular Clocked and Filtered Keystream Generators
In this paper we propose a new key recovery attack on irregular clocked keystream generators where the stream is filtered by a nonlinear Boolean function. We show that the attack is much more efficient than expected from previous analytic methods, and we believe it improves all previous attacks on the cipher model.
متن کاملAlgebraic Attacks on Clock-Controlled Stream Ciphers
Stream ciphers are encryption algorithms used for ensuring the privacy of digital telecommunications. They have been widely used for encrypting military communications, satellite communications, pay TV encryption and for voice encryption of both fixed lined and wireless networks. The current multi year European project eSTREAM, which aims to select stream ciphers suitable for widespread adoptat...
متن کاملConditional Estimators: An Effective Attack on A5/1
Irregularly-clocked linear feedback shift registers (LFSRs) are commonly used in stream ciphers. We propose to harness the power of conditional estimators for correlation attacks on these ciphers. Conditional estimators compensate for some of the obfuscating effects of the irregular clocking, resulting in a correlation with a considerably higher bias. On GSM’s cipher A5/1, a factor two is gaine...
متن کاملThree ways to mount distinguishing attacks on irregularly clocked stream ciphers
Many stream ciphers use irregular clocking to introduce nonlinearity to the keystream. We present three distinguishers on irregularly clocked linear feedback shift registers. The general idea used is to find suitable linear combinations of keystream bits, here called samples, that are drawn from a biased distribution. We describe how to place windows around the estimated positions around member...
متن کاملCorrelation Analysis of the Shrinking Generator
The shrinking generator is a well-known keystream generator composed of two linear feedback shift registers, LFSR1 and LFSR2, where LFSR1 is clock-controlled according to regularly clocked LFSR2. A probabilistic analysis of the shrinking generator which shows that this generator can be vulnerable to a specific fast correlation attack is conducted. The first stage of the attack is based on a rec...
متن کامل