Research And Design Of Stream Cipher Algorithms

Cipher is the core of information security. Stream cipher plays an important role in secure communications.The research of stream cipher is a hostpot in the field of cipher. It is not only used in military and political affairs but also business communicaton. Main content of this paper is as follows.1)Block cipher algorithm can be used as stream cipher when it works in output feedback mode or counter mode. The author discussed the difference between OFB and CTR, and then did two kinds of auto-correlation tests on AES-256, Camellia-128 and SHACAL2. The results indicated that AES-256, Camellia-128 and SHACAL2 had good pseudo-randomness.2)The stream cipher algorithm RC4 has some problems, such as correlative keys generating similar outputs. The improved algorithm RC4* also has the weakness. A modified algorithm called RC4# is put forward in this paper. The RC4# uses a pseudo-randomized S-box and the length of the key, diverts a pseudo-random number. Test results indicate that RC4# avoid that weakness in RC4 and RC4*. Avalanche effect of RC4# is better than RC4 and RC4*. The speed of RC4# is faster than RC4*.3)The stream cipher SEAL applys one-way hash function SHA-1 to generate three tables. The speed of key setup procedure is slow. SEAL is an inappropriate choice for applications which require rapid key setup. A new key setup method based on some ciphers was brought forward in this paper. Test results showed that the speed of the new key setup is eight times faster than old one. The statistical evaluation indicate that SEAL applied new key setup had good pseudo-randomness.4)The methods of design a stream cipher are many and varied. Now some cryptographer focused on research of cipher based on table-driven. The author designed a stream cipher algorithm called ICE based on table-driven and analyzed its security. The TMD attack and Guess- and-Determine attack can not be applied on this algorithm. The algorithm is secure agaist correlation attack, algebraic attack and linear cryptanalysis. The speed of the algorithm ICE is faster than RC4, AES and SNOW2. The dependence test results indicated that the algorithm ICE was complete. The frequency test results indicated that the output of the algorithm had uniformity. Run test, linear complexity test and random excursions test et al results fulfilled the requirements all. So the output of the algorithm had good pseudo-randomness. The security of the cipher was verified by way of statistical evaluation.