merkle_tree_check_update_gadget.hpp

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#ifndef MERKLE_TREE_CHECK_UPDATE_GADGET_HPP_
#define MERKLE_TREE_CHECK_UPDATE_GADGET_HPP_
 
#include <libsnark/common/data_structures/merkle_tree.hpp>
#include <libsnark/gadgetlib1/gadget.hpp>
#include <libsnark/gadgetlib1/gadgets/hashes/crh_gadget.hpp>
#include <libsnark/gadgetlib1/gadgets/hashes/digest_selector_gadget.hpp>
#include <libsnark/gadgetlib1/gadgets/hashes/hash_io.hpp>
#include <libsnark/gadgetlib1/gadgets/merkle_tree/merkle_authentication_path_variable.hpp>
 
namespace libsnark
{
 
template<typename FieldT, typename HashT>
class merkle_tree_check_update_gadget : public gadget<FieldT>
{
private:
    std::vector<HashT> prev_hashers;
    std::vector<block_variable<FieldT>> prev_hasher_inputs;
    std::vector<digest_selector_gadget<FieldT>> prev_propagators;
    std::vector<digest_variable<FieldT>> prev_internal_output;
 
    std::vector<HashT> next_hashers;
    std::vector<block_variable<FieldT>> next_hasher_inputs;
    std::vector<digest_selector_gadget<FieldT>> next_propagators;
    std::vector<digest_variable<FieldT>> next_internal_output;
 
    std::shared_ptr<digest_variable<FieldT>> computed_next_root;
    std::shared_ptr<bit_vector_copy_gadget<FieldT>> check_next_root;
 
public:
    const size_t digest_size;
    const size_t tree_depth;
 
    pb_variable_array<FieldT> address_bits;
    digest_variable<FieldT> prev_leaf_digest;
    digest_variable<FieldT> prev_root_digest;
    merkle_authentication_path_variable<FieldT, HashT> prev_path;
    digest_variable<FieldT> next_leaf_digest;
    digest_variable<FieldT> next_root_digest;
    merkle_authentication_path_variable<FieldT, HashT> next_path;
    pb_linear_combination<FieldT> update_successful;
 
    /* Note that while it is necessary to generate R1CS constraints
       for prev_path, it is not necessary to do so for next_path. See
       comment in the implementation of generate_r1cs_constraints() */
 
    merkle_tree_check_update_gadget(
        protoboard<FieldT> &pb,
        const size_t tree_depth,
        const pb_variable_array<FieldT> &address_bits,
        const digest_variable<FieldT> &prev_leaf_digest,
        const digest_variable<FieldT> &prev_root_digest,
        const merkle_authentication_path_variable<FieldT, HashT> &prev_path,
        const digest_variable<FieldT> &next_leaf_digest,
        const digest_variable<FieldT> &next_root_digest,
        const merkle_authentication_path_variable<FieldT, HashT> &next_path,
        const pb_linear_combination<FieldT> &update_successful,
        const std::string &annotation_prefix);
 
    void generate_r1cs_constraints();
    void generate_r1cs_witness();
 
    static size_t root_size_in_bits();
    /* for debugging purposes */
    static size_t expected_constraints(const size_t tree_depth);
};
 
template<typename FieldT, typename HashT>
void test_merkle_tree_check_update_gadget();
 
} // namespace libsnark
 
#include <libsnark/gadgetlib1/gadgets/merkle_tree/merkle_tree_check_update_gadget.tcc>
 
#endif // MERKLE_TREE_CHECK_UPDATE_GADGET_HPP_