Advances in Cryptology — ASIACRYPT'94

Volume 917 of the series Lecture Notes in Computer Science pp 80-90


On the linear complexity of nonlinearly filtered PN-sequences

  • Amparo Fúster-SabaterAffiliated withLaboratory of Cryptography, Institute of Electronics of Communications (CSIC)
  • , Pino Caballero-GilAffiliated withDepartment of Statistics, Operations Research and Computation, Faculty of Maths, University of La Laguna

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A method of analysis for the linear complexity of nonlinearly filtered PN-sequences is presented. The procedure provides a general lower bound for the linear complexity and an algorithm to improve it. The results obtained are valid for any nonlinear function with a unique term of maximum order and for any maximal-length LFSR. This work, which has as starting point “the root presence test” by Rueppel, is based on the handling of binary strings instead of determinants in a finite field.