ELLIPTIC CURVE GENERATING METHOD AND DEVICE, ELLIPTIC ENCRYPTION SYSTEM AND RECORDING MEDIUM

摘要

A method and device for generating a safe standard elliptic curve that can be converted into a Montgomery elliptic curve, an elliptic encryption system and a recording medium, wherein a curve parameter generating device is constituted which gives a decision condition under which a curve order-related condition is separated from a decision condition whether or not a standard elliptic curve can be converted into a Montgomery elliptic curve and which incorporates a conversion possibility decision unit. For a method of generating a curve having a cofactor of 4, a condition under which a curve order can be divided by 8 is given.