Patent ID: 8265268

Claim:
A converter realized by a computer executing a program stored in a non-transitory information recording medium, said converter using: conversion functions for a domain A, F 1 :A×A→A, F 2 :A×A→A, . . . , F n :A×A→A; a binary exclusive OR operator, XOR:A×A→A; and a predetermined parameter, aεA, and said converter comprising: a generating unit accepting generative inputs, x 1 εA, x 2 εA, . . . , x n εA and generating generative outputs, y 1 εA, y 2 εA, . . . , y n εA using recurrence formulas y 1 =F 1 ( x 1 ,a ), and y i+1 =F i+1 ( x i+1 ,y i )(for 1 ≦i≦n− 1); a key accepting unit accepting key inputs, k 1 εA, k 2 εA, . . . , k n εA, and giving the accepted key inputs as generative inputs to said generating unit; a repetition controller giving the generative outputs from said generating unit as generative inputs to said generating unit, for an “m” (m≧0) number of times, and setting the last generative outputs as a random number sequence, r 1 εA, r 2 εA, . . . , r n εA; a data accepting unit accepting data inputs, d 1 εA, d 2 εA, . . . , d n εA; and a converting unit converting the data inputs into data outputs, e 1 εA, e 2 εA, . . . , e n εA using a formula e i =d i XORr i , and outputting data outputs, wherein each of the conversion functions, F 1 , F 2 , . . . , F n , is a function, ma(.,.), and the function, ma(.,.), is defined by a positive integer M, a positive integer s, a rounding up function ceil(.), and a rounding down function floor(.), as: ma ( x,b )=ceil( xM s /b ) (for 1 ≦x≦b ), and ma ( x,b )=floor( M s ( x−b )/( M s −b ))+1 (for b≦x≦M s ).