Plaintext PIRClient::decode_reply()

in pir_client.cpp [80:135]

• 44 lines of code
• 7 McCabe index (conditional complexity)

Plaintext PIRClient::decode_reply(PirReply reply) {
    uint32_t exp_ratio = pir_params_.expansion_ratio;
    uint32_t recursion_level = pir_params_.d;

    vector<Ciphertext> temp = reply;

    uint64_t t = params_.plain_modulus().value();

    for (uint32_t i = 0; i < recursion_level; i++) {
        cout << "Client: " << i + 1 << "/ " << recursion_level << "-th decryption layer started." << endl; 
        vector<Ciphertext> newtemp;
        vector<Plaintext> tempplain;

        for (uint32_t j = 0; j < temp.size(); j++) {
            Plaintext ptxt;
            decryptor_->decrypt(temp[j], ptxt);
#ifdef DEBUG
            cout << "Client: reply noise budget = " << decryptor_->invariant_noise_budget(temp[j]) << endl; 
#endif
            // multiply by inverse_scale for every coefficient of ptxt
            for(int h = 0; h < ptxt.coeff_count(); h++){
                ptxt[h] *= inverse_scales_[recursion_level -  1 - i]; 
                ptxt[h] %= t; 
            }
            //cout << "decoded (and scaled) plaintext = " << ptxt.to_string() << endl;
            tempplain.push_back(ptxt);

#ifdef DEBUG
            cout << "recursion level : " << i << " noise budget :  ";
            cout << decryptor_->invariant_noise_budget(temp[j]) << endl;
#endif

            if ((j + 1) % exp_ratio == 0 && j > 0) {
                // Combine into one ciphertext.
                Ciphertext combined = compose_to_ciphertext(tempplain);
                newtemp.push_back(combined);
                tempplain.clear();
                // cout << "Client: const term of ciphertext = " << combined[0] << endl; 
            }
        }
        cout << "Client: done." << endl; 
        cout << endl; 
        if (i == recursion_level - 1) {
            assert(temp.size() == 1);
            return tempplain[0];
        } else {
            tempplain.clear();
            temp = newtemp;
        }
    }

    // This should never be called
    assert(0);
    Plaintext fail;
    return fail;
}