Abstract
The nonlinear filter Boolean function of LILI-128 stream cipher generator is studied in this paper. First we measure the complexity of the stream ciphers sequence of LILI-128 stream cipher generator and obtain the shortest bit stream sequence reconstructed Boolean function of nonlinear filter in LILI-128 stream cipher generator. Then the least nonlinear Boolean function of generating stream cipher sequence is reconstructed by clusterig, nonlinear predictive and nonlinear synchronization from shortest bit stream sequence. We have verified the correctness of our reconstruction result by simulating the block diagram of Lili-128 keystream generator using our getting Boolean function and implement designers’ reference module of Lili-128 stream cipher public online, and two methods produce the same synchronous keystream sequence under same initial state, so that our research work proves that the nonlinear Boolean function of LILI-128 stream cipher generator is successfully broken.
Highlights
Our society greatly depends on security of communications, financial transactions, telematic services, internet and mobile networks [1] which in turn present new challenges for protecting the information from unauthorized eavesdropping
We have verified the correctness of our reconstruction result by simulating the block diagram of Lili-128 keystream generator using our getting Boolean function and implement designers’ reference module of Lili-128 stream cipher public online, and two methods produce the same synchronous keystream sequence under same initial state, so that our research work proves that the nonlinear Boolean function of LILI-128 stream cipher generator is successfully broken
The nonlinear sequence is generated through the nonlinear filter function fd with 46 items and the most algebraic 6 orders to withstand all kinds of currently known attack
Summary
Our society greatly depends on security of communications, financial transactions, telematic services, internet and mobile networks [1] which in turn present new challenges for protecting the information from unauthorized eavesdropping. The block ciphers have become widely used technology. As an example AES is a secure block cipher that offers excellent performance on a variety of hardware and software environments. The stream ciphers are widely used in secure communication because of high throughput, less complex hardware circuitry and very little error propagation which has attracted much attention. LILI-128 stream cipher is an example which is designed by Dawson, Clark, Golic, Millan, Penna and Simpson, which submitted to NESSIE (New European Schemes for Signatures, Integrity and Encryption) as a candidate cipher [3]. According to the final report, LILI128 stream cipher was rejected in the first round of NESSIE. In this work we will discuss basic structure and the attack of LILI-128 stream cipher. We study the filter Boolean function of LILI-128 stream cipher generator
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