BTC

Yet another BTC and LTC client.

Why?

To figure out how cryptocurrencies work in general and research mining.

Hashrate

The miner reaches 8-leading-zeros hash in a few seconds.

Unfortunately, such hash rate it is not practical nowadays, since the target has 18 leading zeroes.

Build

Unix-like

It’s a typical CMake project, but requires a few adjustments:

• Latest gcc or cland supporing C++17 or later, and
• OpenSSL from Homebrew (Linux is fine, probably).

I use:

mkdir b && cd b
cmake -DCMAKE_C_COMPILER=gcc-8                            \
      -DCMAKE_CXX_COMPILER=g++-8                          \
      -DCMAKE_BUILD_TYPE=Release                          \
      -DOPENSSL_ROOT_DIR=/usr/local/Cellar/openssl/1.0.2r \
      ..
make

Windows

• Use latest MSVC supporing /std:c++latest, and
• CUDA SDK for OpenCL support.

Before you build the project, you need to prepare dependencies:

git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.bat
./vcpkg.exe integrate install
./vcpkg.exe integrate boost:x64-windows

Then, open the project in MSVC and enjoy compiling.

Running

Before you run the client, you need to find a peer. Run host -a dnsseed.bluematt.me and choose any of them you like, for instance 2406f7cba7cda59:b1b6 (this peer may not be available by the time you read this).

Then, simply run:

src/btc 2406:da18:f7c:4351:ba7c:6da8:da59:b1b6

It will download the whole blockhain (no integrity checks are implemented) and start to mine using the mempool.
Once it reaches the target, it exit(0); the new block won’t be propogated.

GPU mining

To select a GPU as the miner, run src/btc --opencl-info and find your device in the list.
Then, use its number (counting from 0) as the value in --device-id.

For instance, my AMD Radeon Pro 455 is the third in the list, so I pass --device-id 2.

Bugs

The implementation doesn’t count protocol differences, misbehaving peers, and proper sharing GPU with other applications. For instance, once a peer disconnected, the client exits with an exception.

So, if you are brave enough to run this, be aware that:

• Heavy-on-GPU applications should be closed, like Chrome (otherwise all hangs and a hard reboot is required), and
• You may have to run the client multiple times if a peer drops the connection, and you see an error Operation not permitted.

Roadmap

• Mining on CPU (commented out)
• Mining on GPU
• Mining on FPGA
• Integration with ASICs
• Distributed mining
• Integration with mining pools
• Better design of the event loop including support multiple peers and error handling
• Integrity checks for the blockchain
• Integrity guaranties for the local copy of the blockchain