Handbook of Applied Cryptography
Handbook of Applied Cryptography
Two Alerts for Design of Certain Stream Ciphers: Trapped LFSR and Weak Resilient Function over GF(q)
SAC '02 Revised Papers from the 9th Annual International Workshop on Selected Areas in Cryptography
Fast Correlation Attacks: An Algorithmic Point of View
EUROCRYPT '02 Proceedings of the International Conference on the Theory and Applications of Cryptographic Techniques: Advances in Cryptology
Fast Correlation Attack Algorithm with List Decoding and an Application
FSE '01 Revised Papers from the 8th International Workshop on Fast Software Encryption
Higher order correlation attacks, XL algorithm and cryptanalysis of Toyocrypt
ICISC'02 Proceedings of the 5th international conference on Information security and cryptology
Algebraic attacks on stream ciphers with linear feedback
EUROCRYPT'03 Proceedings of the 22nd international conference on Theory and applications of cryptographic techniques
A general formulation of algebraic and fast correlation attacks based on dedicated sample decimation
AAECC'06 Proceedings of the 16th international conference on Applied Algebra, Algebraic Algorithms and Error-Correcting Codes
INDOCRYPT'05 Proceedings of the 6th international conference on Cryptology in India
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This paper proposes an improved approach for cryptanalysis of keystream generators based on a composition of a linear finite state machine (LFSM) and nonlinear mapping. The main feature of the proposed approach is that it is based on identification and selection for further processing certain suitable positions in the given sample so that only the decimated sample elements are relevant for the attacking. In a number of scenarios this yields a significant gain in the performance sometimes at the expense of a longer sample required or/and the pre-processing cost. The proposed approach employs novel methods for constructing the underlying overdefined system of equations relevant for the attacks and solving the system under a set of the hypothesis. Oppositely to the previously reported methods, the proposed ones also identify and use certain characteristics of the LFSM state-transition matrix in order to reduce the nonlinearity of the system. The novel construction of the equations yields a possibility for the trade-off between the required sample, pre-processing and processing complexity of the cryptanalysis. The pre-processing phase of the developed algorithm for cryptanalysis yields a collection of the output bit positions which are suitable for reducing the equations nonlinearity. The processing phase employs the output bits from the identified collection and it includes an exhaustive search over a subset of the secret key bits.