An avalanche block encryption scheme and chaotic block pseudorandom number generator with application in the image encryption

摘要

Based on a stream encryption scheme with avalanche effect, this paper introduces a block encryption scheme with avalanche effect (BESAE), gives the definition of ideal block pseudo random number generators (BPRNG). Using any key stream generated by an ideal 2 word BPRNG with different seed to decrypt the ciphertext encrypted via the ideal BPRNG and the BESAE will generate an avalanche-liked text whose number of “1” codes appear in a probability (2-1)/2. This paper proposes an 8-dimensional discrete chaotic generalized synchronization system. Based on this system, an 8-word long 2 word BPRNG is designed. The key space and the seed space of the BPRNG are larger than 2. Using FIPS 140-2/gneralized FIPS 140-2 test suite tests 100 key streams generated from the 8-word long 2 word BPRNG with different keys (randomly perturbed system parameters and initial condition). The results showed that over 99%/96.9% 2 word streams passed the tests. Using the BPRNG and the BE-SAE encrypts an RGB Tower image. The results suggest that the BPRNG is able to generate the avalanche effects which are similar to those generated via ideal BPRNGs.