Bitcoin's libbitcoinconsensus with Rust bindings

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

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

This project simplifies a 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 consensus library e.g., for a mobile application.

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

Version numbers

We use [slightly abuse] semantic versioning. The first Major.Minor.Patch number tracks the vendored Bitcoin Core code (see below), the second Major.Minor.Patch tracks this crate. For example, if we upgrade the Bitcoin Core code by a Patch version we also bump our Patch version.

One side effect of this is that crates.io shows our release versions in yellow as if they were pre-release versions, this is due to us using a - which, in semantic versioning, implies a pre-release version.

Bitcoin Core subtree

We use a git subtree to vendor the Bitcoin Core code. This can be seen from the following commits that were created using git subtree add --prefix='depend/bitcoin' git@github.com:bitcoin/bitcoin.git v0.19.2 --squash.

f751613e62 Squashed 'depend/bitcoin/' content from commit 204cc0f575
264282188a Merge commit 'f751613e6203770fa94143b9aba1d116512f0ce7' as 'depend/bitcoin'

To use a later version of Bitcoin Core, for example, v0.20.2

git subtree pull --prefix='depend/bitcoin' git@github.com:bitcoin/bitcoin.git v0.20.2 --squash

MSRV

The MSRV of this crate is 1.41.1.

API

The API is very basic, exposing Bitcoin's API as is. This is intentional to keep this project to a minimal footprint and add 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 chosen) 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. The above example is not segwit therefore verify will succeed with any amount.