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)
{
    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);

    return Scalar(value);
}

// Random Oracle (i.e. SHA3_256)
Scalar oracle(const std::string& input)
{
    uint32_t digest_length = SHA256_DIGEST_LENGTH;
    const EVP_MD* algorithm = EVP_sha3_256();
    uint8_t* digest = static_cast<uint8_t*>(OPENSSL_malloc(digest_length));
    
    EVP_MD_CTX* context = EVP_MD_CTX_new();
    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);
    OPENSSL_free(digest);

    return output;
}

Proof::Proof()
{ /* Do nothing */ }

Proof::Proof(std::string hbc)
: hbc(hbc)
{ /* Do nothing */ }

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

std::ostream& operator<<(std::ostream& os, const Proof& output)
{
    if (!output.hbc.empty())
    {
        os << true;
        os << output.hbc.size();
        os << output.hbc;
        return os;
    }

    os << false;

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

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

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

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

    return os;
}

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

        return is;
    }

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

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

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

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

    return is;
}