Generalized Avalanche Test for Stream Cipher Analysis

In this paper we consider tests for avalanche effect in Key sequence generators. In avalanche effect, small changes in input result in large changes in the output. We adapt the Strict Avalanche Criterion (SAC) randomness test proposed by Castro et al in 2005 in their paper in Mathematics and Computers in Simulation to obtain an avalanche test for Key sequence generators. We then propose a Generalized avalanche criterion (GAC) test which includes strict avalanche criterion and other known avalanche criteria. We apply the known avalanche criteria on a toy example and demonstrate that GAC is able to detect a bigger set of related keys as compared to other existing criteria. GAC may prove a useful criterion for analysis of Key sequence generators.