sidestr-header

Block headers for sidestr sidechains, in both families the parent table allows: the stock 80-byte SHA-256d header (beside btc / tbtc4) and Bitcoin Knots' 164-byte v2 header with the tagged-hash-plus-BLAKE2b proof of work (beside xbt / txbt4). Compact targets, the powLimit check siding applies, the BIP-325 block data over each family's serialisation, the version-bit-31 rule, and the fork activation constants of SPEC 3.2.

#![no_std], no allocator, every primitive from RustCrypto (sha2, blake2), no bitcoin crate dependency.

use sidestr_header::{HeaderFamily, Target};

let bytes = hex::decode(
    "0000002000000000000000000000000000000000000000000000000000000000000000003a87d59ecf60ab58ee75948cc39d1bb44ac4285747e64b5a1e7a960d37764cb40e67b26affff7f2002000000",
).unwrap();
let header = HeaderFamily::Stock.decode(&bytes).unwrap();
assert_eq!(header.hash().to_string(),
           "4db37517728bd509c0cb96ee5a2e3e2a77f9e965a092e9f67948b413d453dbc0");
let pow_limit = Target::from_hex("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap();
assert!(header.check_pow(&pow_limit).is_ok());

Why two families

SPEC 3: "everything the overlay does not set is inherited from the parent: header format and proof-of-work hash … Nothing in the document names a header format or a hash; the parent decides both." So a chain's header is the parent's header, and the parent table (SPEC 3.2) has two of them.

Status

0.1.0 — both families decode, encode, hash and check proof of work against the reference to the byte; the BIP-325 block data matches siding's blockData on the live sidestr:dreamlab block 0. Not yet here: the header-chain rules that need a previous header (prev link, committed height, median time past) and the coinbase's BIP 34 height for the stock family — those belong to sidestr-core.

Attribution

This crate is a port, under the same licence, of:

• bitcoin-desktop/schema (AGPL-3.0), commit b8cbf6337c7450fe14ddc5bce00c7280059aab5d: codec/pow/knots-header-v2.js (the v2 proof-of-work pipeline), codec/pow/blake2b.js and codec/hash.js (replaced by RustCrypto), codec/codec.js (expandCompact, the header codec), codec/headers.js (compactFromTarget), schema/overlays/knots-blake2b.jsonld (the v2 layout and its field comments, adapted in the rustdoc), and the test vectors under test/vectors/knots/ — Bitcoin Knots' own block_header_v2.json and real fork headers captured from a Knots 29.4.1 node on 2026-09-05.
• sidestr/spec (AGPL-3.0), Melvin Carvalho, commit 2de40bdac4cba01be0864156a553d8287c22e279: siding/lib/block.mjs (buildBlock's header shape per family, blockData), siding/lib/parents.mjs (the family per parent), siding/lib/chain.mjs (bits = compactFromTarget(powLimit)), and SPEC.md §3, §3.2, §4.
• bitcoin-blake/blaketestnode (AGPL-3.0) is the kernel's reference for the fork chains; nothing was ported from it directly.

What changed in the port: the two hand-written hash functions are replaced by sha2 and blake2; the header is a typed struct per family rather than a schema-driven object; compact targets that Bitcoin Core rejects (negative, overflow) are rejected here where the JS kernel is lenient — unreachable on a valid sidestr chain, where bits is pinned to powLimit.

Licence

AGPL-3.0-only. See LICENSE. This crate is a derivative of AGPL-3.0 code and is not dual-licensed (agentbox ADR-2106).