For the anti-jamming purpose,frequency hopping sequences are required to have a large linear span. In this paper,we firstly give the linear span of a class of optimal frequency hopping sequences. The results show that...For the anti-jamming purpose,frequency hopping sequences are required to have a large linear span. In this paper,we firstly give the linear span of a class of optimal frequency hopping sequences. The results show that the linear span is very small compared with their periods. To improve the linear span,we transform these optimal frequency hopping sequences into new optimal frequency hopping sequences with large linear span by using a general type of permutation polynomials over a finite field. Furthermore,we give the exact values of the linear span of the transformed optimal frequency hopping sequences.展开更多
A new 5-round distinguisher of AES with key whitening is presented by using the properties of its round transformation. Based on this distinguisher,we present new meet-in-the-middle attacks on reduced AES considering ...A new 5-round distinguisher of AES with key whitening is presented by using the properties of its round transformation. Based on this distinguisher,we present new meet-in-the-middle attacks on reduced AES considering the key schedule and the time-memory tradeoff approach. New attacks improve the best known meet-in-the-middle attacks on reduced AES presented at FSE2008.We reduce the time complexity of attacks on 7-round AES-192 and 8-round AES-256 by a factor of at least 28. Moreover,the distinguisher can be exploited to develop the attack on 8-round AES-192.展开更多
基金supported by 973 project (No.2007CB311201)Natural Science Foundation of China (No.60833008)+1 种基金111 project (No.B08038)Foundation of Guangxi Key Lab. of Infor. and Comm. (20902)
文摘For the anti-jamming purpose,frequency hopping sequences are required to have a large linear span. In this paper,we firstly give the linear span of a class of optimal frequency hopping sequences. The results show that the linear span is very small compared with their periods. To improve the linear span,we transform these optimal frequency hopping sequences into new optimal frequency hopping sequences with large linear span by using a general type of permutation polynomials over a finite field. Furthermore,we give the exact values of the linear span of the transformed optimal frequency hopping sequences.
基金supported by the Nature Science Foundation of China under grant 60970119, 60833008the National Basic Research Program of China(973) under grant 2007CB311201the Fundamental Research Funds for the Central Universities under grant K50510010018
文摘A new 5-round distinguisher of AES with key whitening is presented by using the properties of its round transformation. Based on this distinguisher,we present new meet-in-the-middle attacks on reduced AES considering the key schedule and the time-memory tradeoff approach. New attacks improve the best known meet-in-the-middle attacks on reduced AES presented at FSE2008.We reduce the time complexity of attacks on 7-round AES-192 and 8-round AES-256 by a factor of at least 28. Moreover,the distinguisher can be exploited to develop the attack on 8-round AES-192.
