Function CreateAssetSurjectionProof

src/blindpsbt.cpp:39–67

Create surjection proof

// Create surjection proof
bool CreateAssetSurjectionProof(std::vector<unsigned char>& output_proof, const std::vector<secp256k1_fixed_asset_tag>& fixed_input_tags, const std::vector<secp256k1_generator>& ephemeral_input_tags, const std::vector<uint256>& input_asset_blinders, const uint256& output_asset_blinder, const secp256k1_generator& output_asset_tag, const CAsset& asset, size_t num_targets)
{
    int ret;
    // 1 to 3 targets
    size_t inputs_to_select = std::min(num_targets, fixed_input_tags.size());
    unsigned char randseed[32];
    GetStrongRandBytes(randseed, 32);
    size_t input_index;
    secp256k1_surjectionproof proof;
    secp256k1_fixed_asset_tag fixed_output_tag;
    memcpy(&fixed_output_tag, asset.begin(), 32);
    // Find correlation between asset tag and listed input tags
    if (secp256k1_surjectionproof_initialize(secp256k1_blind_context, &proof, &input_index, &fixed_input_tags[0], fixed_input_tags.size(), inputs_to_select, &fixed_output_tag, 100, randseed) == 0) {
        return false;
    }
    // Using the input chosen, build proof
    ret = secp256k1_surjectionproof_generate(secp256k1_blind_context, &proof, &ephemeral_input_tags[0], ephemeral_input_tags.size(), &output_asset_tag, input_index, input_asset_blinders[input_index].begin(), output_asset_blinder.begin());
    assert(ret == 1);
    // Double-check answer
    ret = secp256k1_surjectionproof_verify(secp256k1_blind_context, &proof, &ephemeral_input_tags[0], ephemeral_input_tags.size(), &output_asset_tag);
    assert(ret == 1);

    // Serialize into output witness structure
    size_t output_len = secp256k1_surjectionproof_serialized_size(secp256k1_blind_context, &proof);
    output_proof.resize(output_len);
    secp256k1_surjectionproof_serialize(secp256k1_blind_context, &output_proof[0], &output_len, &proof);
    assert(output_len == output_proof.size());
    return true;
}

bool VerifyBlindAssetProof(const uint256& asset, const std::vector<unsigned char>& proof, const CConfidentialAsset& conf_asset)
{