- Standardness-by-construction for withdrawal outputs
- Eliminates ad-hoc standardness rule implementations in L2s
- Compact representation

Problem Solved:
L2 operators currently risk being unable to process withdrawals if users request non-standard transactions (e.g., oversized OP_RETURN). BOSD ensures outputs are correct-by-construction according to Bitcoin network's standardness rules, abstracting away complex validation logic.

Available on crates.io

Get Involved:

Detailed Specification and Motivation/Rationale: SPECIFICATION.md
Repository: github.com/alpenlabs/bitcoin-bosd
Feedback welcome via GitHub Issues and Discussion; or the mailing list. 

This work emerged from practical challenges faced by myself and Trey Del Bonis (GitHub @delbonis) at Alpen Labs, while building validation logic for processing L2 withdrawals on-chain for Strata: a Bitcoin-native BitVM-based bridge to a ZK-rollup. We believe standardization in this domain will benefit the entire ecosystem by reducing fragmentation and improving interoperability.

The specification is has a CC0 public domain license, and the Rust implementation is MIT/Apache-2.0 double licensed.

The structure of a BOSD consists of:

- 1-byte tag representing a type ID.
- Arbitrary-length cryptographic payload (although practically bounded to like
  80 bytes).

Here's a table for the supported outputs. Also note that we can trivially extend it by adding more prefixes using the type it byte.

```

| Type | Payload Length(s) | Payload Interpretation | Spend Type    | Mainnet Address Prefix |
| ---- | ----------------- | ---------------------- | ------------- | ---------------------- |
| 0    | ..=80             | `OP_RETURN` payload    | (N/A)         | (N/A)                  |
| 1    | 20                | pubkey hash            | P2PKH         | `1...`                 |
| 2    | 20                | script hash            | P2SH          | `3...`                 |
| 3    | 20, 32            | SegWit v0 hash         | P2WPKH, P2WSH | `bc1q...`              |
| 4    | 32                | SegWit v1 public key   | P2TR          | `bc1p...`              |

```

Since we strived for compact representation both in-memory and also over-the-wire, BOSD does not support checksums or any native error correction.

PS: Technically Strata is not a defect L2, since it is a 1-of-N trust-minimized bridge, and not a fully trustless bridge.