EntropyLab

EntropyLab is a self-contained Bitcoin key and wallet calculator designed for offline, air-gapped use. It converts user-supplied entropy, seed phrases, and private keys into wallet recovery information without intentionally sending sensitive data to a server.

Current version: v0.1.3

Official website: entropylab.online

Features

• Accepts dice rolls, coin flips, hexadecimal entropy, BIP39 seed phrases, extended keys, WIF keys, raw private keys, and Casascius mini private keys. All five BIP39 phrase lengths (12, 15, 18, 21, and 24 words) are supported for every entropy entry method.
• Derives BIP39 seeds, BIP32 extended keys, wallet fingerprints, addresses, and Bitcoin Core-compatible descriptors. Each master fingerprint is shown next to its deterministic LifeHash icon so two keys can be told apart at a glance.
• Supports legacy, nested SegWit, native SegWit, and Taproot single-signature address types.
• Supports Mainnet and Testnet wallet derivation, multisignature construction, and PSBT address rendering. Mainnet is selected by default.
• Derives watch-only multisignature wallets from extended public keys without requiring private keys.
• Inspects PSBT v0 transactions, reports PSBT-provided amounts and fees, checks for repeated ECDSA nonces from the same public key, verifies optional Jade anti-exfil (sign-to-contract) transcripts without a key, and can compare supported SegWit v0 SIGHASH_ALL signatures with RFC 6979, including Bitcoin Core-style low-r grinding, in a temporary session.
• Runs a quick barrage of startup sanity checks on the host browser (secure context, CSPRNG, BigInt, UTF-8 encoding, and NFKD normalization). If any check fails, the page is replaced with a failure report listing the failed checks, because wallet output from a broken host cannot be trusted.
• Produces recovery information that can be saved or printed for offline use.
• Exports a Bitcoin Core wallet.dat (SQLite descriptor wallet) with every derived output descriptor already imported — receive and change for each script type, active and ready for address generation. The default download is watch-only; while private recovery material is shown on screen, the export becomes the spending variant (account xprvs as descriptor keys) and the button says so. Generated database files match Bitcoin Core's own record layout byte-for-byte (verified against Bitcoin Core v28.3.0).

Usage

Download the self-contained entropylab.html from the official website or the releases page, transfer it to a trusted computer, disconnect that computer from all networks, and open the file in a modern browser. For sensitive wallet material, use a dedicated air-gapped machine and verify important addresses and descriptors with an independent wallet or signing device before receiving funds.

To build the HTML file yourself, see Building from source.

An online version is available at entropylab.online for convenient access. Do not enter seed phrases, private keys, or other secret wallet material into an internet-connected device; use the downloaded HTML on a trusted air-gapped computer for sensitive operations.

EntropyLab does not generate wallet entropy. The optional BitBox Heads/Tails controls use browser randomness only to choose an equivalent displayed die face: 1–3 all mean Heads and 4–6 all mean Tails, so that numeric choice does not change the resulting BitBox entropy. Wallet security still depends on the quality and secrecy of the entropy, seed phrase, passphrase, or private key supplied by the user.

Building from source

The build imports the cryptographic libraries declared in package.json, bundles them with the application using esbuild, and inlines the result into a single self-contained HTML file. package-lock.json pins the complete dependency tree and the integrity hash of every downloaded package.

Requirements: Node.js 20.19 or newer.

npm ci
npm run build

Build output (generated; CI rebuilds it for every run and commits it back to rock after each merge so the file stays downloadable from the repository):

• entropylab.html — the self-contained application (open this file)

The version is declared once in package.json and substituted into the output at build time. The generated file is gitignored locally; CI builds it before every test run and commits it back to rock after each merge. To remove generated files, run npm run clean.

Project structure

├── assets/                 Static assets (logo, favicon, social card)
├── scripts/
│   ├── build.mjs           Locked-dependency esbuild and HTML assembly
│   └── verify-site.mjs     Site artifact verification (npm run verify)
├── test/
│   ├── browser-instrumentation.html  In-page browser test hooks
│   ├── browser-suite.html            In-page browser test suite
│   ├── browser.test.mjs              Headless-Firefox integration harness
│   ├── browser-check.test.mjs        Tests for the startup browser sanity checks
│   ├── network-check.test.mjs        Tests for the network-check module
│   ├── sqlite-writer.test.mjs        Tests for the SQLite writer (verified with real SQLite)
│   ├── ui-defaults.test.mjs          UI defaults and markup invariants
│   ├── validate.test.mjs             Source and security invariants
│   ├── wallet-export-reference.mjs   Bitcoin Core wallet.dat ground-truth fixture
│   └── wallet-export.test.mjs        Tests for the wallet.dat export module
├── src/
│   ├── index.html          HTML template (markup and document head)
│   ├── assets/             Header logos, inlined as data URIs at build time
│   ├── css/styles.css      Application styles
│   └── js/
│       ├── app.js          Application logic and explicit package imports
│       ├── sqlite-writer.js Minimal SQLite database file writer
│       ├── wallet-export.js Bitcoin Core wallet.dat descriptor export
│       ├── online.js       Hosted-site behavior and header version label
│       ├── network-check.js Network adapter detection and warning
│       ├── browser-check.js Startup browser sanity checks and kill-screen
│       ├── enhanced-inputs.js
│       └── repeat-inputs.js
├── entropylab.html         Compiled application (generated, CI-committed)
└── versions/archived/      Historical releases excluded from the picker

Development and deployment

The toolchain is npm and Node.js (>=20.19). Install the exact dependency tree with npm ci; every local and CI operation is exposed as an npm script:

npm test                    # run all tests, including the headless-Firefox suite
npm run test:ci             # the CI subset: network-check, ui-defaults, source invariants
npm run test:validate       # validate source and security invariants
npm run test:browser        # test crypto, sanitization, networking, exports in headless Firefox
npm run build               # compile src/ into the generated root files
npm run verify              # verify the site artifact (entropylab.html, assets)
npm run ci                  # run the CI test subset, build, and verify in order

GitHub Actions builds the site first, then runs the same test steps for pull requests and pushes to rock, stages the verified site (entropylab.html, assets/) and deploys it to GitHub Pages. After a merge to rock, a final job commits the rebuilt entropylab.html back to the repository so the file stays downloadable; pull requests never carry the generated output, so they stop conflicting on it. The staging step copies the verified entropylab.html to a deployment-only index.html, allowing both the site root and /entropylab.html to serve the same application without committing a second application artifact. CI runs the test suites that need no browser; the headless-Firefox suite runs locally where a Firefox binary is available. Local checks and CI/CD use the same commands; the workflow contains no separate build implementation.

The browser suite runs the assembled application in headless Firefox against a local Node.js HTTP server. It feeds hostile markup and event-handler strings through user-facing fields, verifies the application makes no network requests at runtime, exercises the hosted warning and assets, derives a known wallet through the UI, and inspects both watch-only and private recovery-sheet exports. It also runs the BIP39 and BIP32 published vectors directly against the application code. It is the only part of the toolchain that needs a browser; the server, build, and test harness are dependency-free Node.js.

Security notice

Bitcoin private keys and seed phrases control funds. Review the code, test the tool with known vectors, keep secret material offline, and maintain verified backups. This software is provided without warranty; use it at your own risk.

License

EntropyLab is released into the public domain under The Ooga Booga License — a caveman-speak dedication of the software to the public domain, with the same meaning as The Unlicense: free to copy, modify, publish, use, compile, sell, or distribute, in source or binary form, for any purpose and by any means, with no warranty of any kind. Any and all copyright interest in the software is dedicated to the public at large.