Hold or receive bitcoin without a signing device.
- Save this air-gapped bitcoin calculator to a removable drive and open it on a computer that never goes online.
- Turn dice rolls or a seed you already have into receive addresses.
- Export an xpub and load into Bitcoin Core or any watch-only wallet, and get paid.
- Keep your private keys offline.
Create. Derive. Verify.
You supply dice, cards, hex, a seed, or a key. EntropyLab derives the BIP-39 seed, master fingerprint, xpubs, and receive addresses. It does not generate entropy for you. Nothing leaves this page.
Derivation method
Seed phrase length
24 words use 256 bits of BIP39 entropy.
Dice roll options
Dice rolls (D6)
Derived seed phrase
Master fingerprint
Advanced entry
Measuring this device…
Grind a vanity address from a key you already hold
Walks either the passphrase or the account number until the address matches your prefix. Same key and same counter always give the same address. Key Station matches can be written back; BIP-85 children stay unchanged. Generates no new entropy.
Before you grind
- A vanity passphrase is a BIP39 passphrase: the seed words alone no longer recover the wallet. After Update key, record the passphrase with the same care as the words.
- Matching is Bitcoin mainnet, at the key's first receive address (its own purpose, account, branch, and address index). Update key re-derives Key Station keys; BIP-85 child matches can be copied but do not change the child.
Found passphrases remain in this page only and are never intentionally stored or sent. Memory clearing is best-effort because browsers may retain internal copies; close the page before reconnecting the computer.
Mode
Each candidate is the starting passphrase followed by the counter characters, stretched into a seed (2,048 PBKDF2 rounds) and derived at the key's path. A match is a new passphrase for the same seed words.
Use an existing key
Derive a key on the Keys tab first — the grinder searches that key's passphrase or account index. A key with seed words supports both methods; a root-xprv key supports the derivation grind only.
Selected key
Vanity Formula
Live-filtered to lowercase bech32 characters; each free character multiplies the work by ~32.Matching passphrases
Idle. No range has been ground this session.
Child seeds from a parent key
Same parent, same settings, same child every time. English BIP-39 children match COLDCARD. No new entropy is generated.
Safety notes
Any derived child key that isn't cleared will be available elsewhere in the app wherever choosing an existing key is an option. Anyone with the parent seed, passphrase, application, and index can reproduce them.
Choose a compatible HD-root key from this session, or paste a root extended private key below.
Use an existing key
Path m/83696968'/39'/0'/24'/0'
Build a watch-only multisig
You supply individual co-signer xpubs, choose from keys entered in the Key Station, or paste in an existing multisig wallet descriptor. Verify the derived addresses, or any other info needed to setup a watch-only multisig wallet.
Import existing multisig wallet
Only accepts watch-only public keys; a descriptor carrying private keys will be refused.
Quorum
This will be updated for you if you import an existing multisig above, or you can configure a new multisig directly below.
Multisig requires a quorum of m signatures of n total signing keys to spend.
Uses m/87'/coin'/account' with this Legacy P2SH descriptor. BIP87 account keys are script-agnostic. Leave unchecked for default BIP45 without accounts.
Keep selected keys available for more than one co-signer input. Reused keys need different derivation paths.
Advanced multisig entry
Measuring this device…
Silent Payments, offline
Get an sp1q… address to reuse. Print the URI and DNS text if you want to publish it. Make a sender output or check pasted outputs against your scan key. No chain. No network.
Session keys remain in this page only and are never intentionally stored or sent. Memory clearing is best-effort because browsers may retain internal copies; close the page before reconnecting the computer.
Mode
Use a key from Key Station
Results
Fill in the fields above and run the calculation to see the results here.
No session key. Receive and verify need a seed or root xprv.
See what’s in a transaction
Paste a PSBT or a raw transaction. You’ll see where the coins go, the fee, and the signatures.
A “PSBT” is a Partially Signed Bitcoin Transaction.
Inspect with key (optional)
Add a key to enhance the PSBT inspection features. When a key is entered the inspection results will highlight which transaction outputs belong to that key.
Use a key from Key Station
Session keys remain in this page only and are never intentionally stored or sent. Memory clearing is best-effort because browsers may retain internal copies; close the page before reconnecting the computer.
No session key. Inspect-only mode.
PSBT inspect result
Provide a PSBT and click Inspect to view the details here.
Disable the consensus layer: edits are no longer checked against Bitcoin's rules (transaction sanity, UTXO claims, signatures, witness data) and a violating result builds and exports anyway. The problem list still reports what it finds.
“Insane editing” is for deliberately broken files only.
Editor
Compare with another PSBT
Paste a second PSBT to see what changed relative to the one in the editor. The comparison reads the decoded contents, so reordered maps are not a difference; transaction, signing-state, and metadata changes are reported separately. It describes differences only — it does not judge whether a change is safe.
PSBT comparison result
Paste a second PSBT and click Compare to view the differences here.
Inspect with key
Add a key to check each signature against RFC 6979 and low-r grinding, so an unexpected nonce can be told apart from a deterministic one.
Use a key from Key Station
Session keys remain in this page only and are never intentionally stored or sent. Memory clearing is best-effort because browsers may retain internal copies; close the page before reconnecting the computer.
Jade anti-exfil transcript (optional)
USB Jade only (Green host nonce + opening). QR / sign_psbt does not run anti-exfil yet. BitBox anti-klepto is a different mix — do not paste it here.
Cross-session ECDSA nonce history
Compare this inspection with earlier ECDSA signatures without keeping a PSBT or signature. The versioned file records when each r value was checked, its master fingerprint when available, the raw r value, hashed signing-key and message/source identifiers, and a verification flag. A master fingerprint groups a wallet; the hashed signing-key identifier keeps different child keys distinct. This is correlation-sensitive metadata, so keep it offline.
No nonce history in memory. Inspect a PSBT or upload a history file.
No session key. Inspect-only mode.
ECDSA nonce check result
Provide a PSBT or signed transaction and click Inspect Nonces to view the details here.
Derive a Lightning node key
LND seed → LND node key. BIP-39 seed → LDK node key. Decode only. Does not create a seed. Nothing leaves this page.
No node key derived. Enter a seed phrase and derive.
Seeds and derived keys remain in this page only and are never stored or sent. Memory clearing is best-effort because browsers may retain internal copies; close the page before reconnecting the computer.
Entropy Journal
A local notebook of entropy you already produced. Password is optional. No password means anyone with the file can open it. Not a password manager. Does not generate entropy.
Journal open
No entries yet. Download the journal file after you add one.
The journal lives in this page until you download its file. Password-protected files require the exact password; files created without one can be opened by anyone. Memory clearing is best-effort; close the page before reconnecting the computer.
Notepad
Notes for this sitting. Closing the page throws them away unless you download them.
Key manager
Save key inputs in one .elkeys file. Imports are unchecked until you load and derive again. Uses the Journal password. Nothing leaves the machine.
Ignored keys
Session state
What’s on this page right now. Private material stays hidden unless you tick the box.
This snapshot follows the current stations automatically.
Session log
Last 400 actions, with a time and a fingerprint. No seeds, no keys, no secrets.
Download this with a bug report. It names tools and fingerprints, not seeds.
No events yet.
Sources
Ian Coleman BIP39: github.com/iancoleman/bip39 — pull bip39-standalone.html from Releases, or src/js/index.js, entropy.js, jsbip39.js, wordlist_english.js.
bitaddress.org: github.com/pointbiz/bitaddress.org — pull bitaddress.org.html, or src/ninja.key.js, ninja.detailwallet.js, ninja.paperwallet.js, bitcoinjs-lib.eckey.js.
BitBox02 diceware: roll-the-dice-generate-your-own-seed — lookup table is the BIP39 English list in order.
D++ D8 & D16 method: Roll Your Own Bitcoin Seed Phrase — the published 24-word workflow uses one D8 labeled 1–8 and two hexadecimal D16 dice labeled 0–F per word, then a final D8.
Die Distribution / Fairness Analysis (Pearson’s χ²): How can I test whether a die is fair? — live check while entering rolls, following the Dice Fairness Tester thresholds.
Jade anti-exfil (sign-to-contract): Anti-Exfil: Stopping Key Exfiltration — secp256k1-zkp ecdsa_s2c / anti_exfil_host_verify.
BIP-85 deterministic entropy: bip-0085.mediawiki — HMAC-SHA512 of a fully hardened child; English BIP-39 / WIF / XPRV / HEX / password applications match COLDCARD.
BIP-352 Silent Payments: bips/bip-0352 — reusable sp1q… addresses and unique taproot outputs. Descriptors: BIP-392. Publish URI: BIP-321. DNS name: BIP-353 — this page prints the TXT, it does not resolve names.
Inscription envelopes: docs.ordinals.com/inscriptions — OP_FALSE OP_IF "ord" parser only. This tool does not create inscriptions or number sats.
Important notes
- Your computer may save a copy of your keys to its drive without asking, and the browser can't stop it. For real funds, use an offline computer with an encrypted drive, and turn off hibernation in settings.
- Anything you copy or paste may be kept by clipboard history and synced to your other devices.
- Your keys may stay in memory after you finish, so close the browser and restart the computer. It is a precaution, not a guarantee.
- This page never connects to any network — the network preference choice sets the address formats, key versions, and validation checks the EntropyLab tools use.
- Page translated: Your browser sent this page's text to an online translation service. EntropyLab withholds the seed words, keys and typed secrets it shows, but do not rely on that: turn translation off for this page and use EntropyLab's language menu instead.
Security log
Connection and browser warnings for this session. No secrets recorded.