private_recommendations_utils/secure_comparison_server.cpp

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/*
SeComLib
Copyright 2012-2013 TU Delft, Information Security & Privacy Lab (http://isplab.tudelft.nl/)

Contributors:
Inald Lagendijk (R.L.Lagendijk@TUDelft.nl)
Mihai Todor (todormihai@gmail.com)
Thijs Veugen (P.J.M.Veugen@tudelft.nl)
Zekeriya Erkin (z.erkin@tudelft.nl)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include "secure_comparison_server.h"
//avoid circular includes
#include "secure_comparison_client.h"

namespace SeComLib {
namespace PrivateRecommendationsUtils {

    SecureComparisonServer::SecureComparisonServer (const Paillier &paillierCryptoProvider, const Dgk &dgkCryptoProvider, const std::string &configurationPath) :
        paillierCryptoProvider(paillierCryptoProvider),
        dgkCryptoProvider(dgkCryptoProvider),
        l(Utils::Config::GetInstance().GetParameter<size_t>(configurationPath + ".l")),
        minusThreshold(paillierCryptoProvider.GetEncryptedZero(false)),//set this member to [0], since we won't be using it in this case
        twoPowL(BigInteger(2).GetPow(static_cast<unsigned long>(l))),
        encryptedTwoPowL(paillierCryptoProvider.EncryptInteger(twoPowL)),
        blindingFactorCache(paillierCryptoProvider, ComparisonBlindingFactorCacheParameters(configurationPath + ".BlindingFactorCache", l)),
        dgkComparisonServer(std::make_shared<DgkComparisonServer>(paillierCryptoProvider, dgkCryptoProvider, l)) {
    }

    SecureComparisonServer::SecureComparisonServer (const Paillier &paillierCryptoProvider, const Dgk &dgkCryptoProvider, const BigInteger &similarityTreshold, const std::string &configurationPath) :
        paillierCryptoProvider(paillierCryptoProvider),
        dgkCryptoProvider(dgkCryptoProvider),
        l(Utils::Config::GetInstance().GetParameter<size_t>(configurationPath + ".l")),
        minusThreshold(paillierCryptoProvider.EncryptInteger(-similarityTreshold)),
        twoPowL(BigInteger(2).GetPow(static_cast<unsigned long>(l))),
        encryptedTwoPowL(paillierCryptoProvider.EncryptInteger(twoPowL)),
        blindingFactorCache(paillierCryptoProvider, ComparisonBlindingFactorCacheParameters(configurationPath + ".BlindingFactorCache", l)),
        dgkComparisonServer(std::make_shared<DgkComparisonServer>(paillierCryptoProvider, dgkCryptoProvider, l)) {
    }

    Paillier::Ciphertext SecureComparisonServer::Compare (const Paillier::Ciphertext &a, const Paillier::Ciphertext &b) {
        return this->compare(a, -b);
    }

    Paillier::Ciphertext SecureComparisonServer::Compare (const Paillier::Ciphertext &similarityValue) {
        return this->compare(similarityValue, this->minusThreshold);
    }

    Paillier::Ciphertext SecureComparisonServer::compare (const Paillier::Ciphertext &a, const Paillier::Ciphertext &minusB) {
        Paillier::Ciphertext d = encryptedTwoPowL + a + minusB;

        const BlindingFactorContainer &blindingFactorContainer = this->blindingFactorCache.Pop();

        Paillier::Ciphertext z = d + blindingFactorContainer.encryptedR;

        Paillier::Ciphertext zDivTwoPowL = this->secureComparisonClient.lock()->ComputeZDivTwoPowL(z);

        Paillier::Ciphertext t = this->dgkComparisonServer->Compare(blindingFactorContainer.rModTwoPowL);

        Paillier::Ciphertext gamma = zDivTwoPowL - (blindingFactorContainer.encryptedRDivTwoPowL + t);

        /*
        std::cout << "sim(A,B): "; this->secureComparisonClient.lock()->DebugPaillierEncryption(similarityValue);
        std::cout << "-delta: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(minusThreshold);
        std::cout << "2^l: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(encryptedTwoPowL);
        std::cout << "d: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(d);
        std::cout << "z: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(z);
        std::cout << "z div 2^l: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(zDivTwoPowL);
        std::cout << "r (mod 2^l): " << blindingFactorContainer.rModTwoPowL.ToString(10) << std::endl;
        std::cout << "r div 2^l: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(blindingFactorContainer.encryptedRDivTwoPowL);
        std::cout << "t: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(t);
        std::cout << "gamma: "; this->secureComparisonClient.lock()->DebugPaillierEncryption(gamma);
        */

        return gamma;
    }

    void SecureComparisonServer::SetClient (const std::shared_ptr<SecureComparisonClient> &secureComparisonClient) {
        this->secureComparisonClient = secureComparisonClient;
        this->dgkComparisonServer->SetClient(secureComparisonClient->GetDgkComparisonClient());
    }

    const std::shared_ptr<DgkComparisonServer> &SecureComparisonServer::GetDgkComparisonServer () const {
        return this->dgkComparisonServer;
    }

}//namespace PrivateRecommendationsUtils
}//namespace SeComLib