Research On The Cryptanalysis Of Stream Cipher Grain-128 And ZUC

Stream cipher is an important branch of symmetric crytography,is widely suitable for the high security requirements organs such as military,communication.Compared with block ciphers,stream cipher has the advantage of hardware realize easy and high rates for encrypting and decrypting,having less fault broadcast.Stream cipher is promoted further by European eSTREAM project.Since ZUC algorithm is independently developed by china and the first international standard of cryptographic,so security analysis on ZUC is very significant.This dissertation investigates the techniques for cryptanalysis of stream cipher,with focus on Grain-128 and ZUC.We obtain some main results as follows:?1?After research on the fault attack of Grain-128,and for the three design weaknesses of Grain-128,a key recovery attack on Grain-128 with an intermediate state was proposed.Time complexity and memory complexity of the proposed attack are both O?2⁸?.In order to resist the key recovery attack,we made some improvement on the Grain-128 key-stream generator.The security analysis shows that the improved key-stream generator is secure against the proposed attack.?2?In order to probe into the security of the ZUC algorithm,linear distinguish attack on the ZUC algorithm was proposed.In this paper,we first consider the linear approximation of 2-round nonlinear function F and get linear approximation equation.In order to get the best advantage of distinguisher,we search the best linear masking and the best advantage of the linear approximation equation is 2^-22.6,the best advantage of the distinguisher is about 2^-65.5.The result shows that the key stream generated by ZUC is distinguishable from a random sequence after observing approximately O(2¹³¹)bits.