METHOD AND APPARATUS FOR GENERATING KEY STREAM FOR STREAM CIPHER, S-BOX FOR BLOCK CIPHER AND METHOD FOR SUBSTITUTING INPUT VECTOR USING THE S-BOX

摘要

PURPOSE: A key stream generation method, a device thereof, an s-box for a block cipher, and a substitution method thereof are provided to improve non-linearity and to optimize algebraic immunity by using a log function on a finite field, which bases the primitive element of the finite field. CONSTITUTION: A stream encoding device comprises a key stream generator. The stream encoding device comprises a N-stage linear feedback shift register(11), a nonlinear module(12), and an XOR operator(13). The linear feedback shift register and the nonlinear module constitute the key stream generator for the stream cipher. The nonlinear module is a nonlinear filter generator.