时间：12月2日上午10:30——11:30
地点：下沙校区教学D楼104（理学院党员之家）
Abstract:
A binary span n sequence generated by an n-stage nonlinear feedback shift register (NLFSR) is in a one-to-one correspondence of a de Bruijn sequence. However, how to find a nonlinear feedback function which generates such a sequence constitutes a long standing challenge problem for about five decades since Solomon Golomb's pioneer book, Shift Register Sequences, published in the middle of 60's. Recently, those sequences found important applications in stream cipher design for pervasive computing due to their efficient implementation in both hardware and software. In the hope of finding good span n sequences with large linear span, we use orthogonal functions in polynomial representation, i.e., those functions which produce binary sequences with idea 2-level autocorrelation, such as Welch-Gong transformation and Kasami power functions. Surprisingly, we have discovered many instances of span n sequences with optimal linear span or nearly optimal linear span (i.e., it is at least 2^n-3n for a span sequence with period 2^n-1). In this talk, I will first present some historic development of span n sequences (or equivalently de Bruijn sequences). Then I will introduce our experimental results together with some conjectures, which have been validated for n < 21.
专家简介：
龚光于1985和1990在西安电子科技大学、成都电子科技大学分别获得应用数学硕士及电子工程博士学位；1991-1992在意大利罗马的Fondazione Ugo Bordoni (FUB)的数字通信部从事博士后研究，之后任成都电子科技大学副教授。1995-1998美国南加州大学与著名编码及密码学家、伪随机序列理论奠基人S.W. Golomb合作研究。1998年起在加拿大滑铁卢大学任职，2000担任副教授、2004年晋升为正教授。龚光博士主要研究领域是序列设计、密码和通信安全，在IEEE Trans IT, IEEE Trans Comm, Theoretical Computer Science, IET Information Security， Designs, Codes, and Cryptography等刊物和国际会议上发表200多篇论文，并和著有专著“Signal Design for Good Correlation”（Cambridge University Press, 2005）和“Communication System Security”（CRC, 2012）。
她担任过包括IEEE Transactions on Information Theory在内的几个国际学术刊物的副主编，以及一些国际学术会议的技术委员会委员和主席；获得过一些重要的学术研究奖项，如The Premier's Research Excellence Awards, Ontario, Canada, 2001；NSERC Discovery Accelerator Supplement Award, 2009, Canada；Ontario Research Fund - Research Excellence Award, 2010, Canada；以及Best Paper Award of IEEE ICC 2012。
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