Analysis and design of stream ciphers
Analysis and design of stream ciphers
Correlation VIA linear sequential circuit approximation of combiners with memory
EUROCRYPT'92 Proceedings of the 11th annual international conference on Theory and application of cryptographic techniques
Efficient algorithms for solving overdefined systems of multivariate polynomial equations
EUROCRYPT'00 Proceedings of the 19th international conference on Theory and application of cryptographic techniques
Algebraic attacks on stream ciphers with linear feedback
EUROCRYPT'03 Proceedings of the 22nd international conference on Theory and applications of cryptographic techniques
Extending the resynchronization attack
SAC'04 Proceedings of the 11th international conference on Selected Areas in Cryptography
FSE'05 Proceedings of the 12th international conference on Fast Software Encryption
Reducing the space complexity of BDD-Based attacks on keystream generators
FSE'06 Proceedings of the 13th international conference on Fast Software Encryption
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Stream ciphers are widely used for online-encryption of arbitrarily long data, for example when transmitting speech-data between a mobile phone and a base station. An important class of stream ciphers are combiners with memory, with the E0 generator from the Bluetooth standard for wireless communication being their most prominent example. In this paper, we develop design principles for increasing the resistance of combiners with memory against the most dangerous types of cryptanalytic attacks, namely correlation attacks and algebraic attacks. In the case of algebraic attacks, we introduce the first method to guarantee lower bounds on the attack complexity. Starting from the design of the E0 generator, we combine our results in order to construct ciphers that are simultaneously strengthened against both kinds of attacks. Our analysis shows that small changes in the design of E0 already suffice to improve its security enormously.