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https://github.com/BP-WG/bp-std

Modern & lightweight implementation of bitcoin standards without rust-bitcoin/miniscript dependencies
https://github.com/BP-WG/bp-std

bitcoin descriptor-wallet hd-wallet psbt wallet

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Modern & lightweight implementation of bitcoin standards without rust-bitcoin/miniscript dependencies

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README 

        
# Bitcoin standards implementation libraries



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Modern, minimalistic & standard-compliant wallet-level libraries: an alternative

to `rust-bitcoin` and BDK libraries from [LNP/BP Standards Association][Assoc].



The main goals of the libraries are:



- **fast stabilization of APIs**: the library will be targeting v1.0 version

  within the first year of its development; which should enable downstream

  crates using the library also to stabilize and not spend too much effort

  on changing the integration each time the new version of `bp-wallet` is

  released;

- **no use of private keys**: the library analyzes wallet state using

  descriptors and allows to produce unsigned PSBTs, as well as publish and

  analyze (partially) signed PSBTs - but doesn't provide a signer or a way to

  work with any private key material (seeds, mnemonics, xprivs, private keys);

  PSBT files must be signed with some external signers or hardware wallets;

- **standard-compliance**: the library tries to provide full compliance with

  existing bitcoin standards defined in BIPs and do not use any legacy

  approaches or "blockchain-not-bitcoin" practices (like the ones provided by

  BLIPs);

- **separation of bitcoin consensus and standards**: the consensus-related

  code is not a part of this library; all data structures and business logic

  which may have consensus meaning and is required for a wallet is separated

  into an independent [`bp-primitives`] library (a part of [`bp-core`] library),

  which is planned to be more extensively audited and ossified alongside

  bitcoin protocol (while this library will continue to evolve with better

  APIs and to match new wallet standards);

- **extensive use of descriptors**: library focuses on defining all parts of

  a wallet using descriptors; additionally to script pubkey descriptors it also

  supports xpub descriptors, derivation descriptors, applied to script pubkey

  descriptor as a whole, and input descriptors for RBFs. You can read more on

  specific descriptor types in the [section below](#descriptors);

- **script templates**: the library allows to provide an arbitrary script as

  a part of a descriptor, which allows support for BOLT lightning channel

  transaction and makes it possible to ensure stability in the long run;

  you can read more about script templates vs miniscript below;

- **opinionated high-level wallet abstractions**: the library provide a set

  of high-level wallet data structures abstracting away blockchain-level

  details; helping in writing less boilerplate business logic;

- **APIs usable in all rust projects and in FFI**: the library doesn't use

  async rust, complex callbacks, threads etc., which allows to keep the API

  simple, usable from any rust app (like ones using reactive patterns instead of

  async); at the same time all the data structures of the library are

  `Send + Sync`, meaning that they can be used in any multi-thread or async

  environment;

- **abstracted blockchain data providers**: the library abstracts blockchain

  indexer APIs (Electrum, Esplora, Bitcoin Core etc.) and also provides their

  implementation using this library structures.



## FAQs



### Why not use `rust-bitcoin`?



The library doesn't rely on `rust-bitcoin` crate. The reasons for that are:



- **to keep the functionality set small and wallet-specific**: `rust-bitcoin`

  provides "all in one" solution, covering many parts of bitcoin ecosystem, like

  bitcoin peer-to-peer protocol, not really used by a wallet;

- **to keep API stable**: `rust-bitcoin` with each release significantly breaks

  APIs, being in constant refactoring since early 2022 - a process likely to

  last for few years more; update of wallet libraries after each major change is

  painful and takes a lot of developers time and effort, as well as introduces

  API breaking changes downstream preventing all dependent libraries from

  stabilization;

- **separation of private key material**: in Rust it is impossible to achieve

  constant-time production of secret key material, as well as prevent the

  compiler from copying it all over the machine memory (`zeroise` and other

  approaches doesn't prevent that). Thus, providing secret keys alongside

  other APIs may lead to non-secure design of the wallet and should be avoided;

- **separation of consensus code from standards**: `rust-bitcoin` provides next

  to each other consensus-related structures and higher level wallet

  abstractions, which contradicts to the design decision we are making in this

  library;

- **to introduce strong semantic typing**: for instance, `rust-bitcoin` doesn't

  differentiate different forms of scripts (pubkey, sig, witness etc.), while

  in this library we are using semantic type approach, providing type-safe

  variants for each semantically-distinct entity even if it shares the same

  representation with others.



As one may see from the list, `rust-bitcoin` design and maintenance approach

contradicts to the major aims of this project - in fact, this project was

created by [Maxim Orlovsky][orlovsky] (who was the most active contributor to

`rust-bitcoin` since Q1 2019 till Q2 2022) in order to address these issues

using different set of trade-offs, providing an alternative to `rust-bitcoin`

to those who needs it.



### Why not use miniscript?



Miniscript is great for many purposes, but it can't be used for many cases,

including representation of BOLT-3 lightning channel transaction outputs,

re-use of public key in different branches of pre-taproot scripts [1][ms-1].

Miniscript is also still unstable, having recent changes to the semantic due

to discovered bugs [2][ms-2] [3][ms-3]; meaning that the descriptors created

with miniscript before may not be able to deterministically reproduce the

structure of some wallet UTXOs in a future. Finally, the existing Rust

miniscript implementation [`rust-miniscript`] inherits all `rust-bitcoin`

tradeoffs, and is much more unstable in terms of APIs and semantic. Thus, it was

decided to use this library to provide an alternative to miniscript with

introduction of [script templates][#script-templates] convertible to and from

miniscript representation - but with some externally-provided tools instead

of adding miniscript as a direct dependency here.



### Why not BDK?



BDK is great, but it relies on `rust-bitcoin` and `rust-miniscript` and can't

be used outside of that ecosystem, inheriting all tradeoffs described above.

Since we try to address those trade-offs, we had to create a BDK alternative.



### How this project is related to `descriptor-wallet`?



[Descriptor wallet][descriptor-wallet] was an earlier project by the same

authors trying to address `rust-bitcoin` issues by building on top of it. With

the recent v0.30 `rust-bitcoin` release it became clear that the effort of

adoption to API-breaking changes is much higher than creating a new independent

project from scratch, while at the same time the new project may address

`rust-bitcoin` issues in much more efficient and elegant way. Thus, it was

decided to discontinue `descriptor-wallet` and start the new `bp-wallet` project

instead.



## Design



### Script templates



### Descriptors



## Contributing



Contribution guidelines can be found in [CONTRIBUTING](CONTRIBUTING.md)



## More information



### MSRV



Minimum supported rust compiler version (MSRV) is shown in `rust-version` of `Cargo.toml`.



### Policy on altcoins



Altcoins and "blockchains" other than Bitcoin blockchain/Bitcoin protocols are

not supported and not planned to be supported; pull requests targeting them will

be declined.



### Licensing



The libraries are distributed on the terms of Apache 2.0 opensource license.

See [LICENCE](LICENSE) file for the license details.



[Assoc]: https://lnp-bp.org



[bp-primitives]: https://crates.io/crates/bp-primitives



[bp-core]: https://github.com/BP-WG/bp-core



[orlovsky]: https://github.com/dr-orlovsky



[descriptor-wallet]: https://github.com/BP-WG/descriptor-wallet