secure_face_recognition_utils/dgk_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 "dgk_comparison_server.h"
//avoid circular includes
#include "dgk_comparison_client.h"

namespace SeComLib {
namespace SecureFaceRecognitionUtils {
    DgkComparisonServer::DgkComparisonServer (const Paillier &paillierCryptoProvider, const Dgk &dgkCryptoProvider, const std::string &configurationPath) :
        paillierCryptoProvider(paillierCryptoProvider),
        dgkCryptoProvider(dgkCryptoProvider),
        l(Utils::Config::GetInstance().GetParameter<size_t>(configurationPath + ".l")),
        encryptedMinusTwoPowL(paillierCryptoProvider.EncryptIntegerNonrandom(BigInteger(-1) << static_cast<unsigned long>(l))),
        blindingFactorCache(dgkCryptoProvider, DgkComparisonBlindingFactorCacheParameters(configurationPath, l + 1)) {
    }
    
    Paillier::Ciphertext DgkComparisonServer::ComputeLambda (const std::deque<long> &hatRBits, const BigInteger &s) {

        std::deque<Dgk::Ciphertext> hatDBits = this->dgkComparisonClient.lock()->GetHatDBits();

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

        std::deque<Dgk::Ciphertext> e;

        if (s == hatRBits[l - 1]) {

            if (hatRBits[l - 1] == 0) {
                e.emplace_front((hatDBits[l - 1] - this->dgkCryptoProvider.GetEncryptedOne(false)) * blindingFactorContainer.R[l]);
            }
            else {
                e.emplace_front(hatDBits[l - 1] * blindingFactorContainer.R[l]);//the indexes in R are shifted by one
            }
            e.front() = this->dgkCryptoProvider.RandomizeCiphertext(e.front());
        }
        else {
            e.emplace_front(blindingFactorContainer.encryptedR[l]);//the indexes in encryptedR are shifted by one
        }

        Dgk::Ciphertext sigma = hatRBits[l - 1] == 0 ? hatDBits[l - 1] : (this->dgkCryptoProvider.GetEncryptedOne(false) - hatDBits[l - 1]);
        //can't use size_t because the stop condition requires i = -1
        for (long i = static_cast<long>(this->l - 2); i >= 0; --i) {
            if (s == hatRBits[i]) {
                Dgk::Ciphertext c = hatDBits[i] + sigma;
                
                if (s == 0) {
                    c = c - this->dgkCryptoProvider.GetEncryptedOne(false) + sigma;
                }

                e.emplace_front(c * blindingFactorContainer.R[i + 1]);//the indexes in R are shifted by one
                e.front() = this->dgkCryptoProvider.RandomizeCiphertext(e.front());
            }
            else {
                e.emplace_front(blindingFactorContainer.encryptedR[i + 1]);//the indexes in encryptedR are shifted by one
            }
            
            sigma = sigma + (hatRBits[i] == 0 ? hatDBits[i] : (this->dgkCryptoProvider.GetEncryptedOne(false) - hatDBits[i]));
        }

        if (s == 1) {
            e.emplace_front(blindingFactorContainer.encryptedR[0]);//the indexes in encryptedR are shifted by one
        }
        else {
            e.emplace_front(sigma * blindingFactorContainer.R[0]);//the indexes in R are shifted by one
            e.front() = this->dgkCryptoProvider.RandomizeCiphertext(e.front());//is this really necessary?
        }

        SecurePermutation permutation(e.size());
        permutation.Permute(e);

        Paillier::Ciphertext lambda = this->dgkComparisonClient.lock()->ComputeLambda(e);

        if (s == 0) {
            lambda = this->encryptedMinusTwoPowL - lambda;
        }

        return lambda;
    }

    void DgkComparisonServer::SetClient (const std::shared_ptr<DgkComparisonClient> &dgkComparisonClient) {
        this->dgkComparisonClient = dgkComparisonClient;
    }

}//namespace SecureFaceRecognitionUtils
}//namespace SeComLib