pgp_s2k_functions.hpp

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//---------------------------------------------------------------------------//
// Copyright (c) 2018-2020 Mikhail Komarov <nemo@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
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// 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:
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// The above copyright notice and this permission notice shall be included in all
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//---------------------------------------------------------------------------//
 
#ifndef CRYPTO3_PBKDF_PGP_S2K_FUNCTIONS_HPP
#define CRYPTO3_PBKDF_PGP_S2K_FUNCTIONS_HPP
 
#include <nil/crypto3/pbkdf/detail/pgp_s2k/pgp_s2k_policy.hpp>
 
namespace nil {
    namespace crypto3 {
        namespace pbkdf {
            namespace detail {
                template<typename Hash>
                struct pgp_s2k_functions : public pgp_s2k_policy<Hash> {
                    typedef typename pgp_s2k_policy<Hash>::hash_type hash_type;
 
                    typedef pgp_s2k_policy<Hash> policy_type;
 
                    constexpr static const std::size_t round_constants_size = policy_type::round_constants_size;
                    typedef typename policy_type::round_constants_type round_constants_type;
 
                    static std::uint8_t encode_count(std::size_t iterations) {
                        /*
                    Only 256 different iterations are actually representable in OpenPGP format ...
                    */
                        for (std::size_t c = 0; c < policy_type::round_constants_size; ++c) {
                            const uint32_t decoded_iter = policy_type::round_constants[c];
                            if (decoded_iter >= iterations) {
                                return static_cast<uint8_t>(c);
                            }
                        }
 
                        return 255;
                    }
 
                    static std::size_t decode_count(std::uint8_t encoded_iter) {
                        return policy_type::round_constants[encoded_iter];
                    }
                };
            }    // namespace detail
        }        // namespace pbkdf
    }            // namespace crypto3
}    // namespace nil
 
#endif    // CRYPTO3_PGP_S2K_FUNCTIONS_HPP