method

mul

Ruby latest stable (v2_5_5) - 0 notes - Class: Point

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mul(p1, p2 = v2, p3 = v3) public

Performs elliptic curve point multiplication.

The first form calculates bn1 * point + bn2 * G, where G is the generator of the group of point. bn2 may be omitted, and in that case, the result is just bn1 * point.

The second form calculates bns[0] * point + bns[1] * points[0] + ... + bns[-1] * points[-1] + bn2 * G. bn2 may be omitted. bns must be an array of OpenSSL::BN. points must be an array of OpenSSL::PKey::EC::Point. Please note that points[0] is not multiplied by bns[0], but bns[1].

Show source

static VALUE ossl_ec_point_mul(int argc, VALUE *argv, VALUE self)
{
    EC_POINT *point_self, *point_result;
    const EC_GROUP *group;
    VALUE group_v = rb_attr_get(self, id_i_group);
    VALUE arg1, arg2, arg3, result;
    const BIGNUM *bn_g = NULL;

    GetECPoint(self, point_self);
    GetECGroup(group_v, group);

    result = rb_obj_alloc(cEC_POINT);
    ossl_ec_point_initialize(1, &group_v, result);
    GetECPoint(result, point_result);

    rb_scan_args(argc, argv, "12", &arg1, &arg2, &arg3);
    if (!RB_TYPE_P(arg1, T_ARRAY)) {
        BIGNUM *bn = GetBNPtr(arg1);

        if (!NIL_P(arg2))
            bn_g = GetBNPtr(arg2);
        if (EC_POINT_mul(group, point_result, bn_g, point_self, bn, ossl_bn_ctx) != 1)
            ossl_raise(eEC_POINT, NULL);
    } else {
        /*
         * bignums | arg1[0] | arg1[1] | arg1[2] | ...
         * points  | self    | arg2[0] | arg2[1] | ...
         */
        long i, num;
        VALUE bns_tmp, tmp_p, tmp_b;
        const EC_POINT **points;
        const BIGNUM **bignums;

        Check_Type(arg1, T_ARRAY);
        Check_Type(arg2, T_ARRAY);
        if (RARRAY_LEN(arg1) != RARRAY_LEN(arg2) + 1) /* arg2 must be 1 larger */
            ossl_raise(rb_eArgError, "bns must be 1 longer than points; see the documentation");

        num = RARRAY_LEN(arg1);
        bns_tmp = rb_ary_tmp_new(num);
        bignums = ALLOCV_N(const BIGNUM *, tmp_b, num);
        for (i = 0; i < num; i++) {
            VALUE item = RARRAY_AREF(arg1, i);
            bignums[i] = GetBNPtr(item);
            rb_ary_push(bns_tmp, item);
        }

        points = ALLOCV_N(const EC_POINT *, tmp_p, num);
        points[0] = point_self; /* self */
        for (i = 0; i < num - 1; i++)
            GetECPoint(RARRAY_AREF(arg2, i), points[i + 1]);

        if (!NIL_P(arg3))
            bn_g = GetBNPtr(arg3);

        if (EC_POINTs_mul(group, point_result, bn_g, num, points, bignums, ossl_bn_ctx) != 1) {
            ALLOCV_END(tmp_b);
            ALLOCV_END(tmp_p);
            ossl_raise(eEC_POINT, NULL);
        }

        ALLOCV_END(tmp_b);
        ALLOCV_END(tmp_p);
    }

    return result;
}

mul

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