Crate mk_codec 

mk-codec — reference implementation of the Mnemonic Key (MK) backup format.

Status: v0.1 implementation in progress. Wire format is locked per the closure design at docs/superpowers/specs/2026-04-29-mk1-open-questions-closure-design.md. The bytecode and string-layer encoders/decoders land in subsequent phases of design/IMPLEMENTATION_PLAN_mk_v0_1.md.

See for the design surface:

• design/SPEC_mk_v0_1.md — wire-format spec (post-closure)
• design/DECISIONS.md — rolling decisions log including D-1..D-15 and Q-1..Q-10 closures
• design/IMPLEMENTATION_PLAN_mk_v0_1.md — v0.1 implementation plan
• design/FOLLOWUPS.md — deferred items, pre-BIP-submission audit gates, cross-repo coordination
• bip/bip-mnemonic-key.mediawiki — BIP draft

See for related sibling project:

• bg002h/descriptor-mnemonic — the MD policy-template format and its md-codec reference implementation. MK is designed to engrave alongside MD policy cards for foreign-xpub multisig recovery.

Eventual factoring

Per design/DECISIONS.md D-13, this crate initially forks the BCH primitives from the sibling md-codec. The shared codex32-derived plumbing extracts to a third crate (mc-codex32, likely a third sibling repo) once both formats are implementation-validated; the trigger condition (closure Q-9) is “both md-codec and mk-codec at v1.0 with cross-validated conformance vectors and stable public APIs.” Until then, fork-from-md-codec; both implementations carry their own BCH-primitives copy.

Re-exports

pub use consts::CHUNKED_FRAGMENT_LONG_BYTES;

pub use consts::CHUNKED_FRAGMENT_REGULAR_BYTES;

pub use consts::CROSS_CHUNK_HASH_BYTES;

pub use consts::GENERATOR_FAMILY;

pub use consts::HRP;

pub use consts::MAX_CHUNKS;

pub use consts::MAX_PATH_COMPONENTS;

pub use consts::MK_LONG_CONST;

pub use consts::MK_REGULAR_CONST;

pub use consts::NUMS_DOMAIN;

pub use consts::ORIGIN_FINGERPRINT_BYTES;

pub use consts::POLICY_ID_STUB_BYTES;

pub use consts::SINGLE_STRING_LONG_BYTES;

pub use consts::SINGLE_STRING_REGULAR_BYTES;

pub use consts::XPUB_COMPACT_BYTES;

pub use error::Error;

pub use error::Result;

pub use key_card::KeyCard;

pub use key_card::decode;

pub use key_card::encode;

pub use key_card::encode_with_chunk_set_id;

Modules

bytecode

Bytecode layer — KeyCard ↔ canonical bytecode (pre-chunking).

consts

Locked constants for mk1 per design/SPEC_mk_v0_1.md v0.1.

error

Error type for mk-codec.

key_card

KeyCard — the in-memory representation of a decoded MK card.

string_layer

String layer — KeyCard ↔ Vec<String> (BCH + chunked-header reassembly).

test_vectors

Canonical mk test-vector corpus.