Efficient generation of secure elliptic curves

In many cryptographic applications it is necessary to generate elliptic curves (ECs) whose order possesses certain properties. The method that is usually employed for the generation of such ECs is the so-called Complex Multiplication method. This method requires the use of the roots of certain class field polynomials defined on a specific parameter called the discriminant. The most commonly used polynomials are the Hilbert and Weber ones. The former can be used to generate directly the EC, but they are characterized by high computational demands. The latter have usually much lower computational requirements, but they do not directly construct the desired EC. This can be achieved if transformations of their roots to the roots of the corresponding (generated by the same discriminant) Hilbert polynomials are provided. In this paper we present a variant of the Complex Multiplication method that generates ECs of cryptographically strong order. Our variant is based on the computation of Weber polynomials. We present in a simple and unifying manner a complete set of transformations of the roots of a Weber polynomial to the roots of its corresponding Hilbert polynomial for all values of the discriminant. In addition, we prove a theoretical estimate of the precision required for the computation of Weber polynomials for all values of the discriminant.