Counting Functions and Expected Values for the k-Error Linear Complexity

  • Authors:
  • Wilfried Meidl;Harald Niederreiter

  • Affiliations:
  • Institute of Discrete Mathematics, Austrian Academy of Sciences, Sonnenfelsgasse 19, A-1010, Vienna, Austriaf1wilfried.meidl@oeaw.ac.atf1;Department of Mathematics, National University of Singapore, 2 Science Drive 2, Singapore, 117543

  • Venue:
  • Finite Fields and Their Applications
  • Year:
  • 2002

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Abstract

In cryptology, complexity measures for sequences of elements of a finite field, such as the linear complexity, play an important role. Cryptographically strong sequences or finite strings must not only have a large linear complexity, but also the change of a few terms must not cause a significant decrease of the linear complexity. This requirement leads to the concept of the k-error linear complexity L"n","k(S) of a string S with terms in a finite field F"q and length n. In this article, bounds for the number of strings S of length n with k-error linear complexity L"n","k(S)=c or L"n","k(S)@?c for a given c are established. Under certain conditions on n, k, and c, exact formulas are also determined. On the basis of these results we derive bounds for the expected value of L"n","k(S) for random strings S of length n.