报告人： Tor Helleseth
报告题目：Stream Ciphers and Coding Theory
(流密码和编码理论)
时间：2014年10月28日星期四下午3:30-4:30
地点：数学学院学术报告厅X2511
主讲人简介：Tor Helleseth教授现任挪威Bergen大学教授，是信息科学领域的国际著名学者，一直致力于基础理论和应用研究，在编码理论、信息安全、组合数学等领域都做出了多项开创性和奠基性的工作和独特的贡献，取得举世瞩目的成就。迄今他已发表论文300余篇，其中包括国际信息论旗舰刊物IEEE T. IT论文90余篇，研究深度和广度在国际信息科学领域都是极为罕见的。
Tor Helleseth教授在学术上的卓越成就赢得了国际信息科学界的普遍尊重和崇高的学术声誉，被公认为大师级学者。他1997年当选IEEE Fellow，2004年当选挪威科学院院士，2007-2009任IEEE信息论分会管理委员会理事。
报告内容简介：
Stream ciphers have many applications in modern communication systems. In recent years stream ciphers have received a lot of attention in the eSTREAM project organized by ECRYPT, a European network of Excellence in cryptography.
Important building blocks in many constructions of stream ciphers are the filter generator and the nonlinear combiner generator. These constructions consist of one of more linear feedback shift registers combined with a Boolean function. Based on the content of the involved shift registers the Boolean function provides a keystream.
This talk will survey some attacks on the filter generator and nonlinear combiner generator including the Rønjom-Helleseth attack and some recent generalizations considering the Boolean function as a univariate polynomial. Furthermore a discussion of some connections to coding theory will be provided. The concept of algebraic immunity of Boolean function is shown to be less natural than the new concept of spectral immunity that is determined by coding theoretic properties of a code defined by the Boolean function.
