Converter, encryption/decryption system, multi-stage converter, converting method, multi-stage converting method, program, and information recording medium

Abstract

A converter uses a predetermined parameter a. A generating unit accepts generated inputs x, . . . , x, and generates generated outputs, y, . . . , y, using recurrence formulas, y=F(x, a) and y=F(x, y) (1≦i≦n−1). A key accepting unit accepts key inputs, k, . . . , k, and gives them as generated inputs to said generating unit. A repetition controller gives the generated outputs as generated inputs to said generating unit, for an 'm' (m≧0) number of times, and sets one of the generated outputs to be given at the end as a random number string, r, . . . , r. The data accepting unit accepts data inputs, d, . . . , d. The converting unit converts data using, e=d⋆r, and, outputs data outputs, e, . . . , e. The converter can be used both for encrypting and decrypting data.