Program Listing for File stdlatticeparms.h

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/*
  Header for the standard values for Lattice Parms, as determined by homomorphicencryption.org
 */

#ifndef LBCRYPTO_INC_LATTICE_STDLATTICEPARMS_H
#define LBCRYPTO_INC_LATTICE_STDLATTICEPARMS_H

//  #include "math/math-hal.h"

#include "utils/inttypes.h"

#include <iosfwd>
#include <map>
#include <string>
#include <utility>
#include <vector>

namespace lbcrypto {

// this is the representation of the standard lattice parameters defined in the
// Homomorphic Encryption Standard, as defined by
// http://homomorphicencryption.org

// given a distribution type and a security level, you can get the maxQ for a
// given ring dimension, and you can get the ring dimension given a maxQ

// The code below is very specific to the layout of the DistributionType and
// SecurityLevel enums IF you change them, go look at and change byRing and
// byLogQ

enum DistributionType {
    HEStd_uniform,
    HEStd_error,
    HEStd_ternary,
};

enum SecurityLevel {
    HEStd_128_classic,
    HEStd_192_classic,
    HEStd_256_classic,
    HEStd_128_quantum,
    HEStd_192_quantum,
    HEStd_256_quantum,
    HEStd_NotSet,
};

SecurityLevel convertToSecurityLevel(const std::string& str);
SecurityLevel convertToSecurityLevel(uint32_t num);
std::ostream& operator<<(std::ostream& s, SecurityLevel sl);

class StdLatticeParm {
    DistributionType distType;
    usint ringDim;
    SecurityLevel minSecLev;
    usint maxLogQ;

    // NOTE!!! the declaration below relies upon there being three possible values
    // for the first index (the distribution type), and six possible values for
    // the second index (the security level)
    // The values in the enums, above, meet this criteria
    // it's also important that the different values are numbered from 0-2
    // again, the enums above do this
    // DO NOT change the values of the enums to be anything other than consecutive
    // numbers starting from 0, or this code will break in strange ways, and you
    // will suffer MAKE SURE that the number of entries in the DistributionType
    // enum is == the first index, and MAKE SURE that the number of entries in the
    // SecurityLevel enum is == the second index
    static std::map<usint, StdLatticeParm*> byRing[3][6];
    static std::map<usint, StdLatticeParm*> byLogQ[3][6];

    static std::vector<StdLatticeParm> StandardLatticeParmSets;
    static bool initialized;

public:
    StdLatticeParm(DistributionType distType, usint ringDim, SecurityLevel minSecLev, usint maxLogQ)
        : distType(distType), ringDim(ringDim), minSecLev(minSecLev), maxLogQ(maxLogQ) {}

    static void initializeLookups() {
        for (size_t i = 0; i < StandardLatticeParmSets.size(); i++) {
            StdLatticeParm& s                                                              = StandardLatticeParmSets[i];
            byRing[static_cast<int>(s.distType)][static_cast<int>(s.minSecLev)][s.ringDim] = &s;
            byLogQ[static_cast<int>(s.distType)][static_cast<int>(s.minSecLev)][s.maxLogQ] = &s;
        }
        initialized = true;
    }

    static usint FindMaxQ(DistributionType distType, SecurityLevel minSecLev, usint ringDim) {
        int distTypeIdx  = static_cast<int>(distType);
        int minSecLevIdx = static_cast<int>(minSecLev);
        if (!initialized)
            initializeLookups();
        auto it = byRing[distTypeIdx][minSecLevIdx].find(ringDim);
        if (it == byRing[distTypeIdx][minSecLevIdx].end())
            return 0;
        return it->second->getMaxLogQ();
    }

    static usint FindRingDim(DistributionType distType, SecurityLevel minSecLev, usint curLogQ) {
        if (!initialized)
            initializeLookups();
        usint prev = 0;

        int distTypeIdx  = static_cast<int>(distType);
        int minSecLevIdx = static_cast<int>(minSecLev);
        usint n          = 0;
        for (std::pair<const unsigned int, StdLatticeParm*>& it : byLogQ[distTypeIdx][minSecLevIdx]) {
            if ((curLogQ <= it.second->getMaxLogQ()) && (curLogQ > prev))
                return it.second->getRingDim();
            prev = it.second->getMaxLogQ();
            n    = it.second->getRingDim();
        }
        return 2 * n;
    }

    DistributionType getDistType() const {
        return distType;
    }
    usint getRingDim() const {
        return ringDim;
    }
    SecurityLevel getMinSecLev() const {
        return minSecLev;
    }
    usint getMaxLogQ() const {
        return maxLogQ;
    }
};

} /* namespace lbcrypto */

#endif