PRSONA/prsona/src/proof.cpp

#include "proof.hpp"

/* Altered from answer at
 * https://stackoverflow.com/questions/51144505/generate-sha-3-hash-in-c-using-openssl-library
 */

// Convert the bytes to a single integer, then make that a Scalar
Scalar bytes_to_scalar(
    const std::vector<uint8_t>& bytes,
    size_t lambda)
{
    std::stringstream stream;
    for (uint8_t b : bytes)
        stream << std::setw(2) << std::setfill('0') << std::hex << static_cast<int>(b);

    mpz_class value;
    value.set_str(stream.str(), 16);

    if (lambda < 256)
    {
        mpz_class copy = value;
        mpz_class modVal = 1;
        modVal = modVal << lambda;

        mpz_mod(value.get_mpz_t(), copy.get_mpz_t(), modVal.get_mpz_t());
    }

    return Scalar(value);
}

// Random Oracle (i.e. SHA256)
Scalar oracle(
    const std::string& input,
    size_t lambda)
{
    uint32_t digest_length = SHA256_DIGEST_LENGTH;
    const EVP_MD* algorithm = EVP_sha256();
    uint8_t* digest = static_cast<uint8_t*>(OPENSSL_malloc(digest_length));
    
    EVP_MD_CTX* context = EVP_MD_CTX_create();
    EVP_DigestInit_ex(context, algorithm, NULL);
    EVP_DigestUpdate(context, input.c_str(), input.size());
    EVP_DigestFinal_ex(context, digest, &digest_length);
    EVP_MD_CTX_destroy(context);

    std::vector<uint8_t> digestBytes(digest, digest + digest_length);
    Scalar output = bytes_to_scalar(digestBytes, lambda);
    OPENSSL_free(digest);

    return output;
}

void Proof::clear()
{
    hbc.clear();
    curvepointUniversals.clear();
    curveBipointUniversals.clear();
    challengeParts.clear();
    responseParts.clear();
}

bool Proof::operator==(
    const Proof& b)
{
    bool retval = this->hbc == b.hbc;
    
    retval = retval && this->curvepointUniversals.size() == b.curvepointUniversals.size();
    retval = retval && this->curveBipointUniversals.size() == b.curveBipointUniversals.size();
    retval = retval && this->challengeParts.size() == b.challengeParts.size();
    retval = retval && this->responseParts.size() == b.responseParts.size();

    for (size_t i = 0; retval && i < this->curvepointUniversals.size(); i++)
        retval = retval && this->curvepointUniversals[i] == b.curvepointUniversals[i];

    for (size_t i = 0; retval && i < this->curveBipointUniversals.size(); i++)
        retval = retval && this->curveBipointUniversals[i] == b.curveBipointUniversals[i];

    for (size_t i = 0; retval && i < this->challengeParts.size(); i++)
        retval = retval && this->challengeParts[i] == b.challengeParts[i];

    for (size_t i = 0; retval && i < this->responseParts.size(); i++)
        retval = retval && this->responseParts[i] == b.responseParts[i];

    return retval;
}

std::ostream& operator<<(
    std::ostream& os,
    const Proof& output)
{
    BinaryBool hbc(!output.hbc.empty());
    os << hbc;

    BinarySizeT numElements;

    if (hbc.val())
    {
        numElements.set(output.hbc.length());
        
        os << numElements;
        os << output.hbc;

        return os;
    }

    numElements.set(output.curvepointUniversals.size());
    os << numElements;
    for (size_t i = 0; i < numElements.val(); i++)
        os << output.curvepointUniversals[i];

    numElements.set(output.curveBipointUniversals.size());
    os << numElements;
    for (size_t i = 0; i < numElements.val(); i++)
        os << output.curveBipointUniversals[i];

    numElements.set(output.challengeParts.size());
    os << numElements;
    for (size_t i = 0; i < numElements.val(); i++)
        os << output.challengeParts[i];

    numElements.set(output.responseParts.size());
    os << numElements;
    for (size_t i = 0; i < numElements.val(); i++)
        os << output.responseParts[i];

    return os;
}

std::istream& operator>>(
    std::istream& is,
    Proof& input)
{
    BinaryBool hbc;
    is >> hbc;
    if (hbc.val())
    {
        BinarySizeT numBytes;
        is >> numBytes;
        
        char* buffer = new char[numBytes.val() + 1];
        is.read(buffer, numBytes.val());
        input.hbc = buffer;
        delete buffer;

        return is;
    }

    BinarySizeT numElements;
    is >> numElements;
    for (size_t i = 0; i < numElements.val(); i++)
    {
        Twistpoint x;
        is >> x;
        input.curvepointUniversals.push_back(x);
    }

    is >> numElements;
    for (size_t i = 0; i < numElements.val(); i++)
    {
        TwistBipoint x;
        is >> x;
        input.curveBipointUniversals.push_back(x);
    }

    is >> numElements;
    for (size_t i = 0; i < numElements.val(); i++)
    {
        Scalar x;
        is >> x;
        input.challengeParts.push_back(x);
    }

    is >> numElements;
    for (size_t i = 0; i < numElements.val(); i++)
    {
        Scalar x;
        is >> x;
        input.responseParts.push_back(x);
    }

    return is;
}