Program Listing for File base-pre.cpp

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//==================================================================================
// BSD 2-Clause License
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// Copyright (c) 2014-2022, NJIT, Duality Technologies Inc. and other contributors
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// Author TPOC: contact@openfhe.org
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//==================================================================================
#include "schemebase/base-pre.h"

#include "key/privatekey.h"
#include "key/publickey.h"
#include "cryptocontext.h"
#include "schemebase/base-pke.h"
#include "schemebase/base-scheme.h"

namespace lbcrypto {

template <class Element>
EvalKey<Element> PREBase<Element>::ReKeyGen(const PrivateKey<Element> oldPrivateKey,
                                            const PublicKey<Element> newPublicKey) const {
    auto algo = oldPrivateKey->GetCryptoContext()->GetScheme();
    return algo->KeySwitchGen(oldPrivateKey, newPublicKey);
}

template <class Element>
Ciphertext<Element> PREBase<Element>::ReEncrypt(ConstCiphertext<Element> ciphertext, const EvalKey<Element> evalKey,
                                                const PublicKey<Element> publicKey) const {
    auto algo               = ciphertext->GetCryptoContext()->GetScheme();
    const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersRNS>(ciphertext->GetCryptoParameters());

    Ciphertext<Element> result = ciphertext->Clone();
    std::vector<Element>& cv   = result->GetElements();
    if (publicKey != nullptr) {
        std::shared_ptr<std::vector<Element>> ba = algo->EncryptZeroCore(publicKey);

        cv[0] += (*ba)[0];
        cv[1] += (*ba)[1];
    }

    if ((cryptoParams->GetPREMode() == FIXED_NOISE_HRA) || (cryptoParams->GetPREMode() == NOISE_FLOODING_HRA)) {
        // noiseflooding
        Element enf(cryptoParams->GetFloodingDiscreteGaussianGenerator(), cryptoParams->GetElementParams(),
                    Format::EVALUATION);

        auto noise_scale = cryptoParams->GetNoiseScale();
        cv[0] += noise_scale * enf;
    }
    algo->KeySwitchInPlace(result, evalKey);

    return result;
}

}  // namespace lbcrypto

// the code below is from base-pre-impl.cpp
namespace lbcrypto {

template class PREBase<DCRTPoly>;

}  // namespace lbcrypto