Bitcoin's libbitcoinconsensus with Rust binding

This project builds libbitcoinconsensus library from Bitcoin's C++ sources using cargo and offers Rust binding to its API.

Libbitcoinconsenus allows transaction verification using Bitcoins unique script engine. Bitcoin enabled applications SHOULD use libbitcoinconsensus library to avoid accepting transactions that the Bitcoin network nodes would not.

This project simplifies Rust developer's life by creating the libbitcoinconsensus library with cargo. No need to deal with the archaic C++ toolchain directly.
This also simplifies cross-compiling the consenus library e.g. for a mobile application.

Libbitcoinconsenus refers to code from another library secp256k1. A snapshot of that library is also included into Bitcoin sources, therefore it could be backed into libbitcoinconsenus. A typical Bitcoin enabled application will however want to access further secp256k1 functions. The project rustc-secp256k1 offers a cargo build and Rust bindings, therefore decided to depend on that instead of compiling the Bitcoin embedded sources into libbitcoinconsensus. This introduces a risk, since a difference between the two secp256k1 sources could break consensus with Bitcoin.

Build

This project has a submodule (the Bitcoin Core sources), you have to clone it using:

git clone --recurse-submodules [email protected]:rust-bitcoin/rust-bitcoinconsensus.git

then build it simple with:

cargo build

I verified the build for Linux and OSX. Aleksey Sidorov contributed the windows build. PRs are welcome to extend support for other platforms.

MSRV

The MSRV of this crate is 1.29.0.

The build dependency cc might require a more recent version of the Rust compiler. To ensure compilation with Rust 1.29.0, pin its version in your Cargo.lock with cargo update -p cc --precise 1.0.41. If you're using secp256k1 in a library, to make sure it compiles in CI, you'll need to generate a lockfile first. Example for Travis CI:

before_script:
  - if [ "$TRAVIS_RUST_VERSION" == "1.29.0" ]; then
    cargo generate-lockfile --verbose && cargo update -p cc --precise "1.0.41" --verbose;
    fi

API

The API is very basic, exposing Bitcoin's as is. This is intentional to keep this project minimal footprint and no further runtime dependencies. You will need another Rust library to serialize Bitcoin transactions and scripts.

Verify a single spend (input) of a Bitcoin transaction:

verify (spent_output_script: &[u8], amount: u64, spending_transaction: &[u8], input_index: usize) -> Result<(), Error>

Arguments

• spend_output_script: a Bitcoin transaction output script to be spent
• amount: The spent output amount in satoshis
• spending_transaction: spending Bitcoin transaction, serialized in Bitcoin's on wire format
• input_index: index of the input within spending_transaction

Example

The (randomly choosen) Bitcoin transaction aca326a724eda9a461c10a876534ecd5ae7b27f10f26c3862fb996f80ea2d45d spends one input, that is the first output of 95da344585fcf2e5f7d6cbf2c3df2dcce84f9196f7a7bb901a43275cd6eb7c3f with a value of 630482530 satoshis

The spending transaction in wire format is:

spending = 02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700

The script of the first output of the spent transaction is:

spent = 76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ac

The (pseudo code) call:

verify(spent, 630482530, spending, 0)

should return OK(())

Note that spent amount will only be checked for Segwit transactions. Above example is not segwit therefore verify will succeed with any amount.