A Simplified Method for Computing the Key Equivocation for Additive-Like Instantaneous Block Encipherers

We study the problem of computing the key equivocation rate for secrecy systems with additive-like instantaneous block (ALIB) encipherers. In general it is difficult to compute the exact value of the key equivocation rate for a secrecy system ( f , C ) with ALIB encipherer when the block length n becomes large. In this paper, we propose a simplified method for computing the key equivocation rate for two classes of secrecy systems with ALIB encipherers. 1) The function f is additive-like and the block encipherer C is the set of all n-length key words (sequences) of type P . 2) The function f is additive and the block encipherer C is a linear (n, m) code in the n-dimensional vector space GF(q)n. The method has a potential use for more classes of secrecy systems.