hestdparms.h

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license.

#pragma once

#include "seal/util/defines.h"
#include <cstddef>

namespace seal
{
    namespace util
    {
        /**
        Largest allowed bit counts for coeff_modulus based on the security estimates from
        HomomorphicEncryption.org security standard. Microsoft SEAL samples the secret key
        from a ternary {-1, 0, 1} distribution.
        */
        // Ternary secret; 128 bits classical security
        SEAL_NODISCARD constexpr int seal_he_std_parms_128_tc(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 27;
            case std::size_t(2048):
                return 54;
            case std::size_t(4096):
                return 109;
            case std::size_t(8192):
                return 218;
            case std::size_t(16384):
                return 438;
            case std::size_t(32768):
                return 881;
            }
            return 0;
        }

        // Ternary secret; 192 bits classical security
        SEAL_NODISCARD constexpr int seal_he_std_parms_192_tc(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 19;
            case std::size_t(2048):
                return 37;
            case std::size_t(4096):
                return 75;
            case std::size_t(8192):
                return 152;
            case std::size_t(16384):
                return 305;
            case std::size_t(32768):
                return 611;
            }
            return 0;
        }

        // Ternary secret; 256 bits classical security
        SEAL_NODISCARD constexpr int seal_he_std_parms_256_tc(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 14;
            case std::size_t(2048):
                return 29;
            case std::size_t(4096):
                return 58;
            case std::size_t(8192):
                return 118;
            case std::size_t(16384):
                return 237;
            case std::size_t(32768):
                return 476;
            }
            return 0;
        }

        // Ternary secret; 128 bits quantum security
        SEAL_NODISCARD constexpr int seal_he_std_parms_128_tq(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 25;
            case std::size_t(2048):
                return 51;
            case std::size_t(4096):
                return 101;
            case std::size_t(8192):
                return 202;
            case std::size_t(16384):
                return 411;
            case std::size_t(32768):
                return 827;
            }
            return 0;
        }

        // Ternary secret; 192 bits quantum security
        SEAL_NODISCARD constexpr int seal_he_std_parms_192_tq(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 17;
            case std::size_t(2048):
                return 35;
            case std::size_t(4096):
                return 70;
            case std::size_t(8192):
                return 141;
            case std::size_t(16384):
                return 284;
            case std::size_t(32768):
                return 571;
            }
            return 0;
        }

        // Ternary secret; 256 bits quantum security
        SEAL_NODISCARD constexpr int seal_he_std_parms_256_tq(std::size_t poly_modulus_degree) noexcept
        {
            switch (poly_modulus_degree)
            {
            case std::size_t(1024):
                return 13;
            case std::size_t(2048):
                return 27;
            case std::size_t(4096):
                return 54;
            case std::size_t(8192):
                return 109;
            case std::size_t(16384):
                return 220;
            case std::size_t(32768):
                return 443;
            }
            return 0;
        }

        // Standard deviation for error distribution
        constexpr double seal_he_std_parms_error_std_dev = 3.2;
    } // namespace util
} // namespace seal