Program Listing for File bgvrns-parametergeneration.h

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#ifndef LBCRYPTO_CRYPTO_BGVRNS_PARAMETERGENERATION_H
#define LBCRYPTO_CRYPTO_BGVRNS_PARAMETERGENERATION_H

#include "schemerns/rns-parametergeneration.h"

#include <string>
#include <vector>
#include <memory>
#include <utility>

namespace lbcrypto {

/*
   * Struct that keeps track of all noise estimates necessary to compute moduli.
   *
   * @param Berr is the bound on the error distribution
   * @param Bkey is the bound on the key distribution
   * @param expansionFactor is the expansion factor of the ring
   * @param freshEncryptionNoise is the noise after encryption
   * @param keySwitchingNoise is the noise after key switching
   * @param modSwitchingNoise is the noise after modulus switching
   * @param noisePerLevel is the noise we wish to maintain at each level
   */
struct BGVNoiseEstimates {
    const double Berr;
    const double Bkey;
    const double expansionFactor;
    const double freshEncryptionNoise;
    const double keySwitchingNoise;
    const double modSwitchingNoise;
    const double noisePerLevel;

    BGVNoiseEstimates(const double Berr0, const double Bkey0, const double expansionFactor0,
                      const double freshEncryptionNoise0, const double keySwitchingNoise0,
                      const double modSwitchingNoise0, double noisePerLevel0)
        : Berr(Berr0),
          Bkey(Bkey0),
          expansionFactor(expansionFactor0),
          freshEncryptionNoise(freshEncryptionNoise0),
          keySwitchingNoise(keySwitchingNoise0),
          modSwitchingNoise(modSwitchingNoise0),
          noisePerLevel(noisePerLevel0) {}
};

class ParameterGenerationBGVRNS : public ParameterGenerationRNS {
public:
    virtual ~ParameterGenerationBGVRNS() {}

    /*
   * Method that generates parameters for the BGV RNS scheme.
   *
   * @param cryptoParams contains parameters input by the user
   * @param evalAddCount is the maximum number of additions per level.
   * @param keySwitchCount is the maximum number of key switches per level.
   * @param cyclOrder is the cyclotomic order, which is twice the ring dimension.
   * @param numPrimes Number of CRT moduli.
   * @param firstModSize is the approximate bit size of the first CRT modulus.
   * @param dcrtBits is the approximate bit size of the remaining CRT moduli.
   * @param numPartQ
   * @param multihopQBound
   * @return A boolean.
   */
    bool ParamsGenBGVRNS(std::shared_ptr<CryptoParametersBase<DCRTPoly>> cryptoParams, uint32_t evalAddCount,
                         uint32_t keySwitchCount, usint cyclOrder, usint numPrimes, usint firstModSize, usint dcrtBits,
                         uint32_t numPartQ, usint multihopQBound) const override;

    // SERIALIZATION

    template <class Archive>
    void save(Archive& ar, std::uint32_t const version) const {}

    template <class Archive>
    void load(Archive& ar, std::uint32_t const version) {}

    std::string SerializedObjectName() const {
        return "ParameterGenerationBGVRNS";
    }

private:
    /*
   * Method that computes a security-compliant ring dimension.
   *
   * @param cryptoParams contains parameters input by the user
   * @param qBound is the upper bound on the number of bits in the ciphertext modulus
   * @param cyclOrder is the cyclotomic order, which is twice the ring dimension.
   * @return The ring dimension.
   */
    uint32_t computeRingDimension(std::shared_ptr<CryptoParametersBase<DCRTPoly>> cryptoParams, uint32_t qBound,
                                  usint cyclOrder) const;

    BGVNoiseEstimates computeNoiseEstimates(std::shared_ptr<CryptoParametersBase<DCRTPoly>> cryptoParams,
                                            uint32_t ringDimension, uint32_t evalAddCount, uint32_t keySwitchCount,
                                            uint32_t auxBits, usint numPrimes) const;

    uint64_t getCyclicOrder(const uint32_t ringDimension, const int plainModulus,
                            const ScalingTechnique scalTech) const;

    /*
   * Method that generates moduli for FLEXIBLEAUTOEXT mode for the BGV RNS scheme.
   *
   * @param cryptoParams contains parameters input by the user
   * @param ringDimension is the dimension of the ring (n)
   * @param evalAddCount is the maximum number of additions per level.
   * @param keySwitchCount is the maximum number of key switches per level.
   * @param auxBits is the size of the additional modulus P, used for hybrid key-switching.
   * @param numPrimes Number of CRT moduli.
   * @return A pair containing: 1) a vector with the CRT moduli and 2) the total modulus size to be used for ensuring security compliance.
   */
    std::pair<std::vector<NativeInteger>, uint32_t> computeModuli(
        std::shared_ptr<CryptoParametersBase<DCRTPoly>> cryptoParams, uint32_t ringDimension, uint32_t evalAddCount,
        uint32_t keySwitchCount, uint32_t auxBits, usint numPrimes) const;

    /*
   * Method that initializes the Discrete Gaussian Generator with flooding for PRE.
   *
   * @param cryptoParams contains parameters input by the user
   * @param numPrimes Number of CRT moduli.
   */
    void InitializeFloodingDgg(std::shared_ptr<CryptoParametersBase<DCRTPoly>> cryptoParams, usint numPrimes) const;
};

}  // namespace lbcrypto

#endif