zk/include/nil/crypto3/zk/snark/systems/ppzksnark/r1cs_se_ppzksnark/verifier.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
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#ifndef CRYPTO3_ZK_R1CS_SE_PPZKSNARK_BASIC_VERIFIER_HPP
#define CRYPTO3_ZK_R1CS_SE_PPZKSNARK_BASIC_VERIFIER_HPP
 
#ifdef MULTICORE
#include <omp.h>
#endif
 
#include <nil/crypto3/algebra/multiexp/multiexp.hpp>
#include <nil/crypto3/algebra/multiexp/policies.hpp>
#include <nil/crypto3/algebra/algorithms/pair.hpp>
 
#include <nil/crypto3/zk/snark/schemes/ppzksnark/r1cs_se_ppzksnark/detail/basic_policy.hpp>
 
namespace nil {
    namespace crypto3 {
        namespace zk {
            namespace snark {
 
                template<typename CurveType>
                class r1cs_se_ppzksnark_process_verification_key {
                    typedef detail::r1cs_se_ppzksnark_types_policy<CurveType> policy_type;
 
                public:
                    typedef typename policy_type::verification_key_type verification_key_type;
                    typedef typename policy_type::processed_verification_key_type processed_verification_key_type;
 
                    static inline processed_verification_key_type
                        process(const verification_key_type &verification_key) {
 
                        typename pairing::pairing_policy<CurveType>::g1_precomputed_type 
                            G_alpha_pc = precompute_g1<CurveType>(verification_key.G_alpha);
                        typename pairing::pairing_policy<CurveType>::g2_precomputed_type 
                            H_beta_pc = precompute_g2<CurveType>(verification_key.H_beta);
 
                        processed_verification_key_type processed_verification_key;
                        processed_verification_key.G_alpha = verification_key.G_alpha;
                        processed_verification_key.H_beta = verification_key.H_beta;
                        processed_verification_key.G_alpha_H_beta_ml =
                            miller_loop<CurveType>(G_alpha_pc, H_beta_pc);
                        processed_verification_key.G_gamma_pc = 
                            precompute_g1<CurveType>(verification_key.G_gamma);
                        processed_verification_key.H_gamma_pc = 
                            precompute_g2<CurveType>(verification_key.H_gamma);
                        processed_verification_key.H_pc = 
                            precompute_g2<CurveType>(verification_key.H);
 
                        processed_verification_key.query = verification_key.query;
 
                        return processed_verification_key;
                    }
                };
 
                /*
                 Below are four variants of verifier algorithm for the R1CS SEppzkSNARK.
 
                 These are the four cases that arise from the following two choices:
 
                 (1) The verifier accepts a (non-processed) verification key or, instead, a processed
                 verification key. In the latter case, we call the algorithm an "online verifier".
 
                 (2) The verifier checks for "weak" input consistency or, instead, "strong" input consistency.
                     Strong input consistency requires that |primary_input| = CS.num_inputs, whereas
                     weak input consistency requires that |primary_input| <= CS.num_inputs (and
                     the primary input is implicitly padded with zeros up to length CS.num_inputs).
                 */
 
                template<typename CurveType>
                class r1cs_se_ppzksnark_verifier_weak_input_consistency {
                    typedef detail::r1cs_se_ppzksnark_types_policy<CurveType> policy_type;
 
                public:
                    typedef typename policy_type::primary_input_type primary_input_type;
                    typedef typename policy_type::verification_key_type verification_key_type;
                    typedef typename policy_type::processed_verification_key_type processed_verification_key_type;
                    typedef typename policy_type::proof_type proof_type;
 
                    static inline bool process(const verification_key_type &vk,
                                               const primary_input_type &primary_input,
                                               const proof_type &proof) {
                        return process(
                            r1cs_se_ppzksnark_process_verification_key<CurveType>::process(vk), primary_input, proof);
                    }
 
                    static inline bool process(const processed_verification_key_type &processed_verification_key,
                                               const primary_input_type &primary_input,
                                               const proof_type &proof) {
 
                        bool result = true;
 
                        if (!proof.is_well_formed()) {
                            result = false;
                        }
 
#ifdef MULTICORE
                        const std::size_t chunks = omp_get_max_threads();    // to override, set OMP_NUM_THREADS env
                                                                             // var or call omp_set_num_threads()
#else
                        const std::size_t chunks = 1;
#endif
 
                        typename CurveType::template g1_type<>::value_type G_psi =
                            processed_verification_key.query[0] +
                            algebra::multiexp<algebra::policies::multiexp_method_bos_coster>(
                                processed_verification_key.query.begin() + 1, processed_verification_key.query.end(),
                                primary_input.begin(), primary_input.end(), chunks);
 
                        typename CurveType::gt_type::value_type
                            test1_l = miller_loop<CurveType>(
                                precompute_g1<CurveType>(proof.A + processed_verification_key.G_alpha),
                                precompute_g2<CurveType>(proof.B + processed_verification_key.H_beta)),
                            test1_r1 = processed_verification_key.G_alpha_H_beta_ml,
                            test1_r2 = miller_loop<CurveType>(precompute_g1<CurveType>(G_psi),
                                                                   processed_verification_key.H_gamma_pc),
                            test1_r3 = miller_loop<CurveType>(precompute_g1<CurveType>(proof.C),
                                                                   processed_verification_key.H_pc);
                        typename CurveType::gt_type::value_type test1 = final_exponentiation<CurveType>(
                            test1_l.unitary_inversed() * test1_r1 * test1_r2 * test1_r3);
 
                        if (test1 != CurveType::gt_type::value_type::one()) {
                            result = false;
                        }
 
                        typename CurveType::gt_type::value_type test2_l = miller_loop<CurveType>(
                                                              precompute_g1<CurveType>(proof.A),
                                                              processed_verification_key.H_gamma_pc),
                                                          test2_r = miller_loop<CurveType>(
                                                              processed_verification_key.G_gamma_pc,
                                                              precompute_g2<CurveType>(proof.B));
                        typename CurveType::gt_type::value_type test2 =
                            final_exponentiation<CurveType>(test2_l * test2_r.unitary_inversed());
 
                        if (test2 != CurveType::gt_type::value_type::one()) {
                            result = false;
                        }
 
                        return result;
                    }
                };
 
                template<typename CurveType>
                class r1cs_se_ppzksnark_verifier_strong_input_consistency {
                    typedef detail::r1cs_se_ppzksnark_types_policy<CurveType> policy_type;
 
                public:
                    typedef typename policy_type::primary_input_type primary_input_type;
                    typedef typename policy_type::verification_key_type verification_key_type;
                    typedef typename policy_type::processed_verification_key_type processed_verification_key_type;
                    typedef typename policy_type::proof_type proof_type;
 
                    static inline bool process(const verification_key_type &vk,
                                               const primary_input_type &primary_input,
                                               const proof_type &proof) {
                        return process(
                            r1cs_se_ppzksnark_process_verification_key<CurveType>::process(vk), primary_input, proof);
                    }
 
                    static inline bool process(const processed_verification_key_type &pvk,
                                               const primary_input_type &primary_input,
                                               const proof_type &proof) {
 
                        bool result = true;
 
                        if (pvk.query.size() != primary_input.size() + 1) {
                            result = false;
                        } else {
                            result = r1cs_se_ppzksnark_verifier_weak_input_consistency<CurveType>::process(
                                pvk, primary_input, proof);
                        }
 
                        return result;
                    }
                };
            }    // namespace snark
        }        // namespace zk
    }            // namespace crypto3
}    // namespace nil
 
#endif    // CRYPTO3_ZK_R1CS_SE_PPZKSNARK_BASIC_GENERATOR_HPP