cf45a61070
`cloudhead` on IRC was asking how to properly use
`BlockHeader::validate_pow()` on genesis (or similar) when the
pow_limit field isn't expressible as a compact target (and, thus,
does not actually represent the PoW limit/genesis target). We
swap it for the actual PoW limit by truncating the way a compact
encoding round-trip would.
Note that, in Bitcoin Core, the original value is only ever used
once in its original form:
```
if (bnNew > bnPowLimit) // Note: bnPowLimit is params.powLimit
bnNew = bnPowLimit;
return bnNew.GetCompact();
```
Thus, even if Core adopted our change, as long as there exist no
256-bit integer x which satisfies
`x <= powLimit && x > encoding_roundtrip_truncated(powLimit)` and
`enoding_roundtrip_truncated(x) != powLimit`, the change would have
no impact on consensus.
It is trivial to show that there are no values which are between
the new value
(0x00000000ffff0000000000000000000000000000000000000000000000000000)
and the original value
(0x00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
which can be encoded in compact form, but it is also critically, no
such values will encode to a compact form of anything different than
the new value as the encoding always truncates the low bits, never
rounding up.
|
||
|---|---|---|
| contrib | ||
| examples | ||
| fuzz | ||
| src | ||
| .gitignore | ||
| .travis.yml | ||
| CHANGELOG.md | ||
| Cargo.toml | ||
| LICENSE | ||
| README.md | ||
README.md
Rust Bitcoin Library
Library with support for de/serialization, parsing and executing on data structures and network messages related to Bitcoin.
Supports (or should support)
- De/serialization of Bitcoin protocol network messages
- De/serialization of blocks and transactions
- Script de/serialization
- Private keys and address creation, de/serialization and validation (including full BIP32 support)
- PSBT creation, manipulation, merging and finalization
- Pay-to-contract support as in Appendix A of the Blockstream sidechains whitepaper
For JSONRPC interaction with Bitcoin Core, it is recommended to use rust-bitcoincore-rpc.
Known limitations
Consensus
This library must not be used for consensus code (i.e. fully validating blockchain data). It technically supports doing this, but doing so is very ill-advised because there are many deviations, known and unknown, between this library and the Bitcoin Core reference implementation. In a consensus based cryptocurrency such as Bitcoin it is critical that all parties are using the same rules to validate data, and this library is simply unable to implement the same rules as Core.
Given the complexity of both C++ and Rust, it is unlikely that this will ever be fixed, and there are no plans to do so. Of course, patches to fix specific consensus incompatibilities are welcome.
Documentation
Currently can be found on docs.rs/bitcoin. Patches to add usage examples and to expand on existing docs would be extremely appreciated.
Contributing
Contributions are generally welcome. If you intend to make larger changes please discuss them in an issue before PRing them to avoid duplicate work and architectural mismatches. If you have any questions or ideas you want to discuss please join us in #rust-bitcoin on freenode.
Minimum Supported Rust Version (MSRV)
This library should always compile with any combination of features on Rust 1.22.
Installing Rust
Rust can be installed using your package manager of choice or
rustup.rs. The former way is considered more secure since
it typically doesn't involve trust in the CA system. But you should be aware
that the version of Rust shipped by your distribution might be out of date.
Generally this isn't a problem for rust-bitcoin since we support much older
versions (>=1.22) than the current stable one.
Building
The library can be built and tested using cargo:
git clone git@github.com:rust-bitcoin/rust-bitcoin.git
cd rust-bitcoin
cargo build
You can run tests with:
cargo test
Please refer to the cargo documentation for more detailed instructions.
Pull Requests
Every PR needs at least two reviews to get merged. During the review phase
maintainers and contributors are likely to leave comments and request changes.
Please try to address them, otherwise your PR might get closed without merging
after a longer time of inactivity. If your PR isn't ready for review yet please
mark it by prefixing the title with WIP: .
Policy on Altcoins/Altchains
Patches which add support for non-Bitcoin cryptocurrencies by adding constants to existing enums (e.g. to set the network message magic-byte sequence) are welcome. Anything more involved will be considered on a case-by-case basis, as the altcoin landscape includes projects which frequently appear and disappear, and are poorly designed anyway and keeping the codebase maintainable is a large priority.
In general, things that improve cross-chain compatibility (e.g. support for cross-chain atomic swaps) are more likely to be accepted than things which support only a single blockchain.
Release Notes
See CHANGELOG.md.
Licensing
The code in this project is licensed under the Creative Commons CC0 1.0 Universal license.