Some Open Problems on Periods of Recent Pseudorandom Sequence Generators in Stream Ciphers
主 题: Some Open Problems on Periods of Recent Pseudorandom Sequence Generators in Stream Ciphers
报告人: Guang Gong (龚光) (University of Waterloo )
时 间: 2009-11-17 上午10:00 - 11:00
地 点: 理科一号楼 1490
According to the theory of Shannon's one-time-pad secure communication system, pseudorandom sequences employed in stream cipher should have large periods. Due to recent algebraic attacks on symmetric key crypto algorithms, it is desired to use nonlinear feedback shift registers (NLFSR) as pseudorandom sequence/number generators (PRG) in stream cipher. However, the problem on periods on nonlinear feedback shift registers has been an open problem for more than 50 decades. In this talk, I will present three types of PRGs. First type is to investigate special feedback functions for achieving large periods, the second type is to use linear feedback shift registers to control NLFSRs, and the third type is to random feedback functions in NLFSRs. Examples include WG and NLFSR trace pseudorandom generators, Grain-like pseudorandom generators and Trivium-like pseudorandom generators. The open problems on their respective periods of those generators will be addressed.