BGN2/bgn2/src/keygen.cpp

#include "keygen.hpp"

extern const curvepoint_fp_t bn_curvegen;   
extern const twistpoint_fp2_t bn_twistgen;

void keygen(PublicKey& public_key, PrivateKey& private_key)
{
    Scalar a1, b1, c1, d1, a2, b2, c2, d2;
    
    while (true)
    {
        a1.set_random();
        b1.set_random();
        c1.set_random();

        if (a1 != 0)
        {
            d1 = (b1 * c1 + Scalar(1)) / a1;
            break;
        }
    }

    while (true)
    {
        a2.set_random();
        b2.set_random();
        c2.set_random();

        if (a2 != 0)
        {
            d2 = (b2 * c2 + Scalar(1)) / a2;
            break;
        }   
    }

    private_key.set(a1, b1, c1, d1, a2, b2, c2, d2);
    
    Scalar r1, r2, r3, r4;
    r1.set_random();
    r2.set_random();
    r3.set_random();
    r4.set_random();

    curvepoint_fp_t g_part1, g_part2, g_a1, g_b1;
    g_part1 = r1 * bn_curvegen;
    g_part2 = r2 * bn_curvegen;
    g_a1 = a1 * bn_curvegen;
    g_b1 = b1 * bn_curvegen;
    Bipoint<curvepoint_fp_t> full_g(g_part1, g_part2);
    Bipoint<curvepoint_fp_t> full_g1(g_a1, g_b1);

    twistpoint_fp2_t h_part1, h_part2, h_a2, h_b2;
    h_part1 = r3 * bn_twistgen;
    h_part2 = r4 * bn_twistgen;
    h_a2 = a2 * bn_twistgen;
    h_b2 = b2 * bn_twistgen;
    Bipoint<twistpoint_fp2_t> full_h(h_part1, h_part2);
    Bipoint<twistpoint_fp2_t> full_h1(h_a2, h_b2);

    full_g.make_affine();
    full_g1.make_affine();
    full_h.make_affine();
    full_h1.make_affine();
        
    public_key.set(full_g, full_h, full_g1, full_h1);
}