Mimir

Mimir is a one-page, offline builder for a deliberately small Bitcoin Script policy. Register up to five compressed public keys, then describe up to five alternative spending clauses by choosing keyholders, a K-of-N signature threshold, and an optional absolute UTC date. Mimir emits the exact native SegWit v0 P2WSH Bitcoin Script, address, script bytes, and recovery metadata.

Restricted Direct Script

Mimir does not generate arbitrary Bitcoin Script and does not use Miniscript. The complete policy language is:

POLICY = CLAUSE 1 OR CLAUSE 2 OR ... OR CLAUSE 5

CLAUSE = [optional absolute CLTV date] AND [one key or K-of-N multisig]

The compiler emits this as a literal, right-nested conditional:

OP_IF
    CLAUSE 1
OP_ELSE
    OP_IF
        CLAUSE 2
    OP_ELSE
        CLAUSE 3
    OP_ENDIF
OP_ENDIF

There is no Boolean rewriting, key factoring, or hidden policy optimization. Every authored clause becomes one Script branch. If a public key is selected in several clauses, it appears several times in the Script. The formatted ASM is therefore intended to remain directly auditable against the clause editor.

Single-key clauses use OP_CHECKSIG. Threshold clauses use the standard K <keys...> N OP_CHECKMULTISIG form. Delayed clauses prepend the Core-signable sequence <timestamp> OP_CHECKLOCKTIMEVERIFY OP_VERIFY. Alternative branches use minimal 0 and 1 witness selectors documented in the exported manifest.

The implemented surface provides:

• one to five valid compressed secp256k1 public keys;
• one to five alternative clauses;
• one signature threshold and at most one absolute date per clause;
• deliberate reuse of keys across any clauses;
• live, formatted Bitcoin Script ASM and exact witness-script hex;
• Mainnet, Testnet, Signet, and Regtest P2WSH addresses;
• branch-selector, signature-order, and CHECKMULTISIG dummy metadata;
• deterministic canonical JSON export; and
• no private-key, seed, xpub, derivation, signing, persistence, or network input.

The concise implementation contract is mimir_v8_spec.md. The former mimir_v7_spec.md remains available as the historical contract for the incompatible mimir-direct-p2wsh-v1 byte layout.

Run locally

Node.js 22.13 or newer is required.

npm install
npm run dev

Open http://localhost:3000. If your system still uses Node 20:

npm exec --yes --package=node@22 -- npm run dev

All application code and assets are local. Policy state stays in volatile page memory, and the production content security policy disables outbound network connections.

Validate

npm test

The tests build and render the application, enumerate all 160 possible single-clause key-set/threshold/timing shapes through five keys, and interpret the generated bytes symbolically for every signer subset and relevant time boundary. Multi-clause tests cover repeated and partially overlapping key sets.

The planned independent execution matrix is documented in BITCOIN_CORE_REGTEST_TEST_PLAN.md.

Safety status

Mimir emits native P2WSH, not Taproot. For OP_CHECKMULTISIG, the spending witness must include the consensus-required empty dummy item and signatures in public-key order. A delayed branch requires transaction nLockTime at least equal to its timestamp and a non-final nSequence on the spending input.

The default npm test suite provides strong compiler and offline transaction checks; it does not start or mutate Bitcoin Core. The opt-in test:regtest:quick campaign executes 100 funded policies and 400 positive/negative outcomes against a Bitcoin Core Regtest node. Before mainnet use, complete the independent exhaustive matrix, reproduce the witness-script bytes and address with independent tooling, and retain the policy JSON with the recovery setup. The planned Bitcoin Core funding/recovery command, OP_RETURN metadata, and dust transaction workflow are not implemented yet.