Patent ID: 7548618

Claim:
A computer readable medium having stored thereon a converter using: an “n” (n≧1) number of conversion functions, F 1 , F 2 , . . . , F n : A×A→A, with respect to a domain 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 , x 2 , . . . , x n εA, and generating generative outputs, y 1 , y 2 , . . . , y n εA, using recurrence formulas, y 1 =F 1 ( x 1 ,a ), and y i+1 =F i+1 ( x i+1 ,x i ) (for 1≦ i≦n− 1); a key accepting unit accepting key inputs, k 1 , k 2 , . . . , 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 , r 2 , . . . , r n εA; a data accepting unit accepting data inputs, d 1 , d 2 , . . . , d n εA; and a converting unit converting the data inputs into data outputs, e 1 , e 2 , . . . , e n εA using a formula e i =d i XOR r i (1≦ i≦n ), and outputting the data outputs; and wherein at least one of the conversion functions, F 1 , F 2 , . . . F n , is either a function, ma(•,•), or an inverse function of ma(•,•), ma −1 (•,•), and wherein the function, ma(•,•), is defined, by positive integers M, s, “M”-number system rounding up function, ceil(•), and “M”-number system 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 ), and the inverse function, ma −1 (•,•), is defined as: ma −1 ( y,b )= x 1 (for q<x 1 ), and ma −1 ( y,b )= x 2 (for x 1 ≦q ) where x 1 =floor( M −s by ), x 2 =ceil(( M −s b− 1) y+M s ), and q=b ( x 2 −M s )/( b−M −s ).