Protecting against security attack

Abstract

A communication device having a private key and configured to implement an elliptic curve security mechanism for successful operation of which it: (a) receives a first value from another device, (b) computes a second value as the scalar multiplication of the first value with its private key and (c) returns that second value for use by the other device; the mechanism being such that the first value defines a pair of coordinates representing a first point and the second value defines a pair of coordinates representing a second point and being such that the first value is valid only if it lies on an elliptic curve of predefined form; the device being configured to implement the mechanism by the steps of: receiving data as the first value; making a first evaluation as to whether the first value is a singular point with respect to the elliptic curve; computing the second value as the scalar multiplication of the first value with the private key; making a second evaluation as to whether the second value lies on the elliptic curve; and returning the second value only if the first evaluation is false and the second evaluation is true.

Dependencies are inferred from the claim text.