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| Content Provider | Springer Nature Link |
|---|---|
| Author | Qi, Wen Feng Tian, Tian |
| Copyright Year | 2012 |
| Abstract | Recently nonlinear feedback shift registers (NFSRs) have frequently been used as building blocks for designing stream ciphers. Let NFSR (g) be an m-stage NFSR with characteristic function $${g=x_{0}\oplus g_{1}(x_{1},\cdots ,x_{m-1})\oplus x_{m}}$$ . Up to now there has been no known method to determine whether the family of output sequences of the NFSR (g), denoted by S(g), contains a sub-family of sequences that are exactly the output sequences of an NFSR(f) of stage n < m. This paper studies affine cases, that is, finding an affine function f such that S(f) is a subset of S(g). If S(g) contains an affine sub-family S(f) whose order n is close to m, then a large number of sequences generated by the NFSR (g) have low linear complexities. First, we give two methods to bound the maximal order of affine sub-families included in S(g). Experimental data indicate that if S(g) contains an affine sub-family of order not smaller than m/2, then the upper bound given in the paper is tight. Second, we propose two algorithms to solve affine sub-families of a given order n included in S(g), both of which aim at affine sub-families with the maximal order. Algorithm 1 is applicable when n is close to m, while the feasibility of Algorithm 2 relies on the distribution of nonlinear terms of g. In particular, if Algorithm 2 works, then its computation complexity is less than that of Algorithm 1 and it is quite efficient for a number of cases. |
| Ending Page | 181 |
| Page Count | 19 |
| Starting Page | 163 |
| File Format | |
| ISSN | 09251022 |
| e-ISSN | 15737586 |
| Journal | Designs, Codes and Cryptography |
| Issue Number | 1 |
| Volume Number | 71 |
| Language | English |
| Publisher | Springer US |
| Publisher Date | 2012-07-15 |
| Publisher Place | Boston |
| Access Restriction | One Nation One Subscription (ONOS) |
| Subject Keyword | Information and Communication, Circuits Data Structures, Cryptology and Information Theory Stream ciphers Discrete Mathematics in Computer Science Nonlinear feedback shift registers Data Encryption Families of NFSR sequences Shift register sequences and sequences over finite alphabets Coding and Information Theory Cryptography Combinatorics |
| Content Type | Text |
| Resource Type | Article |
| Subject | Applied Mathematics Discrete Mathematics and Combinatorics Theoretical Computer Science Computer Science Applications |
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