blueprint/include/nil/crypto3/zk/components/algebra/curves/weierstrass/element_g2.hpp

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//---------------------------------------------------------------------------//
// Copyright (c) 2018-2021 Mikhail Komarov <nemo@nil.foundation>
// Copyright (c) 2020-2021 Nikita Kaskov <nbering@nil.foundation>
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//---------------------------------------------------------------------------//
// @file Declaration of interfaces for G2 components.
//
// The components verify curve arithmetic in G2 = E'(F) where E'/F^e: y^2 = x^3 + A' * X + B'
// is an elliptic curve over F^e in short Weierstrass form.
//---------------------------------------------------------------------------//
 
#ifndef CRYPTO3_ZK_BLUEPRINT_WEIERSTRASS_G2_COMPONENT_HPP
#define CRYPTO3_ZK_BLUEPRINT_WEIERSTRASS_G2_COMPONENT_HPP
 
#include <memory>
 
#include <nil/crypto3/algebra/algorithms/pair.hpp>
 
#include <nil/crypto3/zk/components/component.hpp>
#include <nil/crypto3/zk/components/algebra/curves/detail/mnt4.hpp>
#include <nil/crypto3/zk/components/algebra/curves/detail/mnt6.hpp>
 
#include <nil/crypto3/zk/components/blueprint_variable.hpp>
 
namespace nil {
    namespace crypto3 {
        namespace zk {
            namespace components {
 
                using namespace nil::crypto3::algebra::pairing;
 
                template<typename CurveType>
                class element_g2 : public component<typename CurveType::scalar_field_type> {
 
                    using underlying_field_type = typename CurveType::scalar_field_type;
 
                    using field_type = typename CurveType::pairing::fp_type;
 
                    using fqe_type = typename CurveType::pairing::pair_curve_type::pairing::fqe_type;
                    using fqk_type = typename CurveType::pairing::pair_curve_type::pairing::fqk_type;
 
                    using component_policy = basic_curve_component_policy<CurveType>;
 
                public:
                    std::shared_ptr<typename component_policy::Fqe_variable_type> X;
                    std::shared_ptr<typename component_policy::Fqe_variable_type> Y;
 
                    blueprint_linear_combination_vector<field_type> all_vars;
 
                    element_g2(blueprint<field_type> &bp) : component<field_type>(bp) {
                        X.reset(new typename component_policy::Fqe_variable_type(bp));
                        Y.reset(new typename component_policy::Fqe_variable_type(bp));
 
                        all_vars.insert(all_vars.end(), X->all_vars.begin(), X->all_vars.end());
                        all_vars.insert(all_vars.end(), Y->all_vars.begin(), Y->all_vars.end());
                    }
                    element_g2(blueprint<field_type> &bp,
                               const typename CurveType::pairing::pair_curve_type::template g2_type<>::value_type &Q) :
                        component<field_type>(bp) {
                        typename CurveType::pairing::pair_curve_type::template g2_type<>::value_type Q_copy = Q.to_affine();
 
                        X.reset(new typename component_policy::Fqe_variable_type(bp, Q_copy.X));
                        Y.reset(new typename component_policy::Fqe_variable_type(bp, Q_copy.Y));
 
                        all_vars.insert(all_vars.end(), X->all_vars.begin(), X->all_vars.end());
                        all_vars.insert(all_vars.end(), Y->all_vars.begin(), Y->all_vars.end());
                    }
 
                    void generate_r1cs_witness(
                        const typename CurveType::pairing::pair_curve_type::template g2_type<>::value_type &Q) {
                        typename CurveType::pairing::pair_curve_type::template g2_type<>::value_type Qcopy = Q.to_affine();
 
                        X->generate_r1cs_witness(Qcopy.X);
                        Y->generate_r1cs_witness(Qcopy.Y);
                    }
 
                    // (See a comment in r1cs_ppzksnark_verifier_component.hpp about why
                    // we mark this function noinline.) TODO: remove later
                    static std::size_t __attribute__((noinline)) size_in_bits() {
                        return 2 * typename component_policy::Fqe_variable_type::size_in_bits();
                    }
                    static std::size_t num_variables() {
                        return 2 * typename component_policy::Fqe_variable_type::num_variables();
                    }
                };
 
                template<typename CurveType>
                class element_g2_is_well_formed : public component<typename CurveType::scalar_field_type> {
                    typedef typename CurveType::pairing::fp_type field_type;
                    using fqe_type = typename CurveType::pairing::pair_curve_type::pairing::fqe_type;
                    using fqk_type = typename CurveType::pairing::pair_curve_type::pairing::fqk_type;
 
                    using component_policy = basic_curve_component_policy<CurveType>;
 
                public:
                    element_g2<CurveType> Q;
 
                    std::shared_ptr<typename component_policy::Fqe_variable_type> Xsquared;
                    std::shared_ptr<typename component_policy::Fqe_variable_type> Ysquared;
                    std::shared_ptr<typename component_policy::Fqe_variable_type> Xsquared_plus_a;
                    std::shared_ptr<typename component_policy::Fqe_variable_type> Ysquared_minus_b;
 
                    std::shared_ptr<typename component_policy::Fqe_sqr_component_type> compute_Xsquared;
                    std::shared_ptr<typename component_policy::Fqe_sqr_component_type> compute_Ysquared;
                    std::shared_ptr<typename component_policy::Fqe_mul_component_type> curve_equation;
 
                    element_g2_is_well_formed(blueprint<field_type> &bp, const element_g2<CurveType> &Q) :
                        component<field_type>(bp), Q(Q) {
                        Xsquared.reset(new typename component_policy::Fqe_variable_type(bp));
                        Ysquared.reset(new typename component_policy::Fqe_variable_type(bp));
 
                        compute_Xsquared.reset(
                            new typename component_policy::Fqe_sqr_component_type(bp, *(Q.X), *Xsquared));
                        compute_Ysquared.reset(
                            new typename component_policy::Fqe_sqr_component_type(bp, *(Q.Y), *Ysquared));
 
                        Xsquared_plus_a.reset(new typename component_policy::Fqe_variable_type(
                            (*Xsquared) + CurveType::pairing::pair_curve_type::a));
                        Ysquared_minus_b.reset(new typename component_policy::Fqe_variable_type(
                            (*Ysquared) + (-CurveType::pairing::pair_curve_type::b)));
 
                        curve_equation.reset(new typename component_policy::Fqe_mul_component_type(
                            bp, *(Q.X), *Xsquared_plus_a, *Ysquared_minus_b));
                    }
 
                    void generate_r1cs_constraints() {
                        compute_Xsquared->generate_r1cs_constraints();
                        compute_Ysquared->generate_r1cs_constraints();
                        curve_equation->generate_r1cs_constraints();
                    }
                    void generate_r1cs_witness() {
                        compute_Xsquared->generate_r1cs_witness();
                        compute_Ysquared->generate_r1cs_witness();
                        Xsquared_plus_a->evaluate();
                        curve_equation->generate_r1cs_witness();
                    }
                };
            }    // namespace components
        }        // namespace zk
    }            // namespace crypto3
}    // namespace nil
 
#endif    // CRYPTO3_ZK_BLUEPRINT_WEIERSTRASS_G2_COMPONENT_HPP