weighted_shamir.hpp

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//---------------------------------------------------------------------------//
// Copyright (c) 2020-2021 Mikhail Komarov <nemo@nil.foundation>
// Copyright (c) 2020-2021 Ilias Khairullin <ilias@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
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in all
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//---------------------------------------------------------------------------//
 
#ifndef CRYPTO3_PUBKEY_WEIGHTED_SHAMIR_SSS_HPP
#define CRYPTO3_PUBKEY_WEIGHTED_SHAMIR_SSS_HPP
 
#include <nil/crypto3/pubkey/secret_sharing/shamir.hpp>
 
namespace nil {
    namespace crypto3 {
        namespace pubkey {
            template<typename Group>
            struct weighted_shamir_sss : public shamir_sss<Group> {
                typedef sss_weighted_basic_policy<Group> basic_policy;
                typedef shamir_sss<Group> base_type;
            };
 
            template<typename Group>
            struct public_share_sss<weighted_shamir_sss<Group>> {
                typedef weighted_shamir_sss<Group> scheme_type;
                typedef public_share_sss<shamir_sss<Group>> part_public_share_type;
                typedef std::pair<std::size_t, std::vector<part_public_share_type>> public_share_type;
                typedef typename scheme_type::indexes_type indexes_type;
                typedef typename public_share_type::first_type index_type;
                typedef typename public_share_type::second_type value_type;
                typedef public_share_type data_type;
 
                public_share_sss() = default;
 
                public_share_sss(std::size_t i, std::size_t w, std::size_t threshold_number) : t(threshold_number) {
                    public_share.first = i;
                    assert(scheme_type::check_participant_index(get_index()));
                    assert(scheme_type::check_weight(i, w));
                    for (std::size_t j = 1; j <= w; ++j) {
                        public_share.second.emplace_back(i * t + j);
                        assert(indexes.emplace(public_share.second.back().get_index()).second);
                    }
                }
 
                template<typename PartPublicShares>
                public_share_sss(std::size_t i, std::size_t threshold_number, const PartPublicShares &i_public_shares) :
                    public_share_sss(i, threshold_number, std::cbegin(i_public_shares), std::cend(i_public_shares)) {
                }
 
                template<typename PartPublicShareIt>
                public_share_sss(const std::size_t i, std::size_t threshold_number, PartPublicShareIt first,
                                 PartPublicShareIt last) :
                    t(threshold_number) {
                    public_share.first = i;
                    assert(scheme_type::check_participant_index(get_index()));
                    for (auto iter = first; iter != last; ++iter) {
                        public_share.second.emplace_back(*iter);
                        assert(indexes.emplace(public_share.second.back().get_index()).second);
                    }
                }
 
                inline index_type get_index() const {
                    return public_share.first;
                }
 
                inline const value_type &get_value() const {
                    return public_share.second;
                }
 
                inline const data_type &get_data() const {
                    return public_share.second;
                }
 
                inline const indexes_type &get_indexes() const {
                    return indexes;
                }
 
                inline std::size_t get_threshold_number() const {
                    return t;
                }
 
                inline std::size_t get_weight() const {
                    return std::size(indexes);
                }
 
                bool operator==(const public_share_sss &other) const {
                    return this->public_share == other.public_share;
                }
 
                bool operator<(const public_share_sss &other) const {
                    return this->get_index() < other.get_index();
                }
 
                inline part_public_share_type
                    to_shamir(const typename scheme_type::weights_type &confirmed_weights) const {
                    auto confirmed_indexes = scheme_type::get_indexes(confirmed_weights, t);
 
                    typename scheme_type::public_element_type part_share = scheme_type::public_element_type::zero();
                    for (const auto &public_share_j : public_share.second) {
                        part_share = part_share +
                                     public_share_j.get_value() *
                                         scheme_type::eval_basis_poly(confirmed_indexes, public_share_j.get_index());
                    }
 
                    return part_public_share_type(public_share.first, part_share);
                }
 
            private:
                std::size_t t;
                indexes_type indexes;
                public_share_type public_share;
            };
 
            template<typename Group>
            struct share_sss<weighted_shamir_sss<Group>> {
                typedef weighted_shamir_sss<Group> scheme_type;
                typedef share_sss<shamir_sss<Group>> part_share_type;
                typedef std::pair<std::size_t, std::vector<part_share_type>> share_type;
                typedef typename scheme_type::indexes_type indexes_type;
                typedef typename share_type::first_type index_type;
                typedef typename share_type::second_type value_type;
                typedef share_type data_type;
 
                share_sss() = default;
 
                share_sss(std::size_t i, std::size_t w, std::size_t threshold_number) : t(threshold_number) {
                    share.first = i;
                    assert(scheme_type::check_participant_index(get_index()));
                    assert(scheme_type::check_weight(i, w));
                    for (std::size_t j = 1; j <= w; ++j) {
                        share.second.emplace_back(i * t + j);
                        assert(indexes.emplace(share.second.back().get_index()).second);
                    }
                }
 
                inline index_type get_index() const {
                    return share.first;
                }
 
                inline const value_type &get_value() const {
                    return share.second;
                }
 
                inline const data_type &get_data() const {
                    return share;
                }
 
                inline const indexes_type &get_indexes() const {
                    return indexes;
                }
 
                inline std::size_t get_threshold_number() const {
                    return t;
                }
 
                inline std::size_t get_weight() const {
                    return std::size(indexes);
                }
 
                operator public_share_sss<scheme_type>() const {
                    using To = public_share_sss<scheme_type>;
 
                    return To(share.first, t, share.second);
                }
 
                bool operator==(const share_sss &other) const {
                    return this->share == other.share;
                }
 
                bool operator<(const share_sss &other) const {
                    return this->get_index() < other.get_index();
                }
 
                //
                //  0 <= k < t
                //
                inline void update(const typename scheme_type::coeff_type &coeff, std::size_t exp) {
                    for (auto &share_j : share.second) {
                        share_j.update(coeff, exp);
                    }
                }
 
                inline part_share_type to_shamir(const typename scheme_type::weights_type &confirmed_weights) const {
                    auto confirmed_indexes = scheme_type::get_indexes(confirmed_weights, t);
 
                    typename scheme_type::private_element_type part_share = scheme_type::private_element_type::zero();
                    for (const auto &share_j : share.second) {
                        part_share = part_share + share_j.get_value() * scheme_type::eval_basis_poly(
                                                                            confirmed_indexes, share_j.get_index());
                    }
 
                    return part_share_type(share.first, part_share);
                }
 
            private:
                std::size_t t;
                indexes_type indexes;
                share_type share;
            };
 
            template<typename Group>
            struct secret_sss<weighted_shamir_sss<Group>> {
                typedef weighted_shamir_sss<Group> scheme_type;
                typedef typename scheme_type::private_element_type secret_type;
                typedef typename scheme_type::indexes_type indexes_type;
                typedef secret_type value_type;
 
                template<typename Shares>
                secret_sss(const Shares &shares) : secret_sss(std::cbegin(shares), std::cend(shares)) {
                }
 
                template<typename ShareIt>
                secret_sss(ShareIt first, ShareIt last) : secret(reconstruct_secret(first, last)) {
                }
 
                template<typename Shares>
                secret_sss(const Shares &shares, const indexes_type &indexes) :
                    secret_sss(std::cbegin(shares), std::cend(shares), indexes) {
                }
 
                template<typename ShareIt>
                secret_sss(ShareIt first, ShareIt last, const indexes_type &indexes) :
                    secret(reconstruct_secret(first, last, indexes)) {
                }
 
                inline const value_type &get_value() const {
                    return secret;
                }
 
                bool operator==(const secret_sss &other) const {
                    return this->secret == other.secret;
                }
 
            private:
                template<typename ShareIt,
                         typename std::enable_if<
                             std::is_same<typename std::remove_cv<typename std::remove_reference<
                                              typename std::iterator_traits<ShareIt>::value_type>::type>::type,
                                          share_sss<scheme_type>>::value,
                             bool>::type = true>
                static inline secret_type reconstruct_secret(ShareIt first, ShareIt last) {
                    BOOST_CONCEPT_ASSERT((boost::InputIteratorConcept<ShareIt>));
 
                    typename share_sss<scheme_type>::share_type::second_type _shares;
                    for (auto iter = first; iter != last; iter++) {
                        std::copy(std::cbegin(iter->get_value()), std::cend(iter->get_value()),
                                  std::back_inserter(_shares));
                    }
 
                    return reconstruct_secret(std::cbegin(_shares), std::cend(_shares),
                                              scheme_type::get_indexes(std::cbegin(_shares), std::cend(_shares)));
                }
 
                template<typename ShareIt,
                         typename std::enable_if<
                             std::is_same<typename std::remove_cv<typename std::remove_reference<
                                              typename std::iterator_traits<ShareIt>::value_type>::type>::type,
                                          typename share_sss<scheme_type>::part_share_type>::value,
                             bool>::type = true>
                static inline secret_type reconstruct_secret(ShareIt first, ShareIt last, const indexes_type &indexes) {
                    BOOST_CONCEPT_ASSERT((boost::InputIteratorConcept<ShareIt>));
 
                    secret_type secret = secret_type::zero();
                    for (auto it = first; it != last; it++) {
                        secret = secret + it->get_value() * scheme_type::eval_basis_poly(indexes, it->get_index());
                    }
 
                    return secret;
                }
 
                secret_type secret;
            };
 
            template<typename Group>
            struct deal_shares_op<weighted_shamir_sss<Group>> {
                typedef weighted_shamir_sss<Group> scheme_type;
                typedef share_sss<scheme_type> share_type;
                typedef std::vector<share_type> shares_type;
                typedef shares_type internal_accumulator_type;
                typedef shares_type result_type;
 
                static inline void init_accumulator(internal_accumulator_type &acc, std::size_t n, std::size_t t,
                                                    const typename scheme_type::weights_type &weights) {
                    assert(n == std::distance(std::cbegin(weights), std::cend(weights)));
                    assert(scheme_type::check_threshold_value(t, n));
 
                    for (const auto &w_i : weights) {
                        acc.emplace_back(w_i.first, w_i.second, t);
                    }
                }
 
                static inline void update(internal_accumulator_type &acc, std::size_t exp,
                                          const typename scheme_type::coeff_type &coeff) {
                    for (auto shares_iter = std::begin(acc); shares_iter != std::end(acc); ++shares_iter) {
                        shares_iter->update(coeff, exp);
                    }
                }
 
                static inline result_type process(internal_accumulator_type &acc) {
                    return acc;
                }
            };
 
            template<typename Group>
            struct reconstruct_secret_op<weighted_shamir_sss<Group>> {
                typedef weighted_shamir_sss<Group> scheme_type;
                typedef share_sss<scheme_type> share_type;
                typedef secret_sss<scheme_type> secret_type;
                typedef std::vector<share_type> internal_accumulator_type;
                typedef secret_type result_type;
 
            public:
                static inline void init_accumulator() {
                }
 
                static inline void update(internal_accumulator_type &acc, const share_type &share) {
                    acc.emplace_back(share);
                }
 
                static inline result_type process(internal_accumulator_type &acc) {
                    return acc;
                }
            };
        }    // namespace pubkey
    }        // namespace crypto3
}    // namespace nil
 
#endif    // CRYPTO3_PUBKEY_WEIGHTED_SHAMIR_SSS_HPP