Patent ID: 8046582

Claim:
A key generation apparatus for generating a finite field F q , a three-dimensional manifold A(x, y, s, t) defined as having degrees of freedom of three dimensions of a set of solutions of simultaneous equations, which is used as a public key for signature verification, is expressed by an x-coordinate, a y-coordinate, a parameter s, and a parameter t, and is defined on the finite field F q , and a section which is used as a secret key for signature generation and is one of surfaces of the three-dimensional manifold A(x, y, s, t), x-coordinate and y-coordinate of the section being expressed by functions of the parameter s and the parameter t, comprising: a processor configured to: generate a first 2-variable polynomial λ x (s, t) for the parameter s and the parameter t defined on the finite field F q ; generate a second 2-variable polynomial λ y (s, t) which is divisible by the first 2-variable polynomial λ x (s, t) and is defined on the finite field F q ; generate two 2-variable polynomials u x (s, t) and v x (s, t) for the parameter s and the parameter t defined on the finite field F q so that a difference {u x (s, t)−v x (s, t)} between the two 2-variable polynomials equals the first 2-variable polynomial λ x (s, t); generate two 2-variable polynomials u y (s, t) and v y (s, t) for the parameter s and the parameter t defined on the finite field F q so that a difference {u y (s, t)−v y (s, t)} between the two 2-variable polynomials equals the second 2-variable polynomial λ y (s, t); generate a section D 1 : (x, y, s, t)=(u x (s, t), u y (s, t), s, t) which has the generated 2-variable polynomial u x (s, t) as an x-coordinate, and the 2-variable polynomial u y (s, t) as a y-coordinate, and a section D 2 : (x, y, s, t)=(v x (s, t), v y (s, t), s, t) which has the generated 2-variable polynomial v x (s, t) as an x-coordinate, and the generated 2-variable polynomial v y (s, t) as a y-coordinate; and generate a polynomial of the three-dimensional manifold A(x, y, s, t) which includes the section D 1 and the section D 2 .