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6 MIN READ

Multisig, deep dive.
No single point of failure.

A single hardware wallet is a single point of failure. Lose the seed, coerce the owner, burn down the house, and the coins are gone. Multisig splits signing authority across several devices in several locations. Below $25K, one hardware wallet and a good inheritance plan is usually enough. Above it, multisig is how serious holders sleep at night.

READING TIME: 9 MIN

Not financial or legal advice. Multisig adds operational complexity. Misconfigured multisig has lost more coins than any exchange hack. Test with small amounts first. Service pricing and terms marked [VERIFY] should be checked current.

THE SHORT VERSION

Multisig is a Bitcoin wallet that requires M-of-N signatures from different keys to spend. 2-of-3 is the most common setup. You need 2 of the 3 keys to authorize a transaction. Losing 1 key is fine; losing 2 is terminal. You also need the wallet descriptor (a small file) alongside the keys - a seed alone cannot recover a multisig wallet. Use 3 different hardware-wallet brands, store the keys in 3 different physical locations, store the descriptor alongside each key, and test recovery with a small amount before trusting real savings to it.

What multisig actually is

A multisig wallet requires M-of-N signatures from different keys to spend. The most common configuration is 2-of-3: three keys exist, and any two of them together can authorize a transaction. No single key can spend alone. The third key is a backup.

Other configurations exist (3-of-5 for higher-value stacks, 2-of-2 for joint spousal control), but 2-of-3 is the sweet spot for most individual holders. It tolerates one lost key, requires compromise of two separate devices to steal, and is simple enough to actually operate.

Why you would use it

  • No single point of failure. Lose a seed, destroy a device, forget a passphrase - as long as two of three keys remain, your coins are recoverable.
  • Inheritance planning. Distribute keys across trusted family, an attorney, and a service. No single person can spend, and any two together can.
  • Geographic redundancy. A fire, flood, or theft at one location does not cost you the coins.
  • Coercion resistance. If someone physically forces you to hand over a wallet, they cannot spend without keys that are elsewhere. The attack surface for a $5 wrench shifts dramatically.

PSBT (Partially Signed Bitcoin Transactions)

Multisig transactions are signed in multiple steps. The format that carries an in-progress transaction between devices is the PSBT - Partially Signed Bitcoin Transaction. BIP174.

1
Coordinator builds the transaction
Sparrow or another multisig coordinator assembles the unsigned transaction (inputs, outputs, fees) and exports it as a PSBT file.
2
First device signs
Load the PSBT onto the first hardware wallet (SD card, QR code, USB). The device adds its signature and exports a new PSBT with one signature.
3
Second device signs
Load the partially-signed PSBT onto the second hardware wallet. Repeat until M signatures exist.
4
Broadcast
Coordinator finalizes the PSBT and broadcasts it through your node.

Setting up 2-of-3 in Sparrow, step by step

A pragmatic walkthrough. This is the workflow I would recommend after doing it myself with a single hardware wallet and now considering a move up.

  1. Buy 3 hardware wallets from different brands. For example Coldcard Mk4, Trezor Safe 3, and Foundation Passport. Using different brands protects you against a single-vendor firmware bug or supply-chain compromise.
  2. Each device generates its own seed. Record each seed on a separate steel backup. Never take a photo. Never store digitally.
  3. Export xpubs from each device. Every hardware wallet has an export option for its extended public key. Save all three xpubs.
  4. In Sparrow: File -> New Wallet -> Multi Signature -> 2 of 3. Import the three xpubs. Sparrow assembles the multisig wallet.
  5. Save the wallet descriptor. Sparrow exports a PDF with the descriptor. This file describes the multisig structure. Without it, the three individual seeds cannot recover the wallet. Print it. Back it up with every key.
  6. Send a test. Transfer $20 to the multisig wallet. Sign with 2 of 3 devices. Broadcast. Confirm it arrives and that the change returns correctly. Only after this round-trip succeeds is the setup "real."
CRITICAL

The wallet descriptor is as important as the seeds. Seeds alone cannot recover a multisig wallet, because the wallet structure is the descriptor. Print the descriptor. Store a copy with every seed. Losing all copies of the descriptor means losing the coins even if all three seeds survive.

Key storage - geographic distribution

A conservative distribution for 2-of-3:

  • Key 1. At home in a fireproof safe.
  • Key 2. At a trusted family member's house, ideally in a different state.
  • Key 3. In a bank safe deposit box, or held by an attorney or estate service.

All three locations should also store a copy of the wallet descriptor. A single lost seed is recoverable with the other two keys plus the descriptor. A lost descriptor with intact seeds is still recoverable if you have the xpubs written down. But a lost descriptor with no xpub records is not recoverable.

Testing recovery before you need it

The most important step most people skip. Wipe one of the hardware wallets. Recover it from its seed. Re-import the three xpubs and the descriptor into Sparrow. Sign a small test transaction with the recovered device plus one other. Broadcast.

Only after this full round-trip succeeds should you trust the setup with real savings. Every multisig horror story ends with "I assumed it would work and never tested it." Do not be that story.

Collaborative custody services - comparison

UNCHAINED CAPITAL
2-of-3 with partner key
Unchained holds one of the three keys. You hold the other two. Around $120/year base tier [VERIFY]. Texas-based, well-established, transparent about the model. IRA option available.
CASA COVENANT
3-of-5 with recovery service
Higher tier. Casa holds one or two keys, you hold three or four, plus a mobile app key. Multiple service tiers. Inheritance service included. Premium pricing [VERIFY].
DIY (NO SERVICE)
All three keys yourself
Cheapest. Maximum sovereignty. Requires more operational discipline and a rock-solid inheritance plan. No one to call if something goes wrong.

Multisig and inheritance - the coordination problem

The beneficiary of a multisig Bitcoin stack needs two things: enough keys (or the ability to coordinate with whoever holds them), AND the wallet descriptor. Without the descriptor, the keys alone are not enough.

This is where Unchained and Casa shine: their service knows how to coordinate an inheritance. They verify identity, provide the descriptor, and help the beneficiary produce the signatures. DIY multisig requires very careful estate planning, including written instructions the heir can follow without any prior Bitcoin experience.

See inheritance for the full framework.

When to graduate to multisig

Rough threshold: $25,000+ long-term stack, or any level where losing a single seed would feel genuinely devastating. Under $25K, a single hardware wallet with a strong inheritance plan (a written guide for your heirs, a metal seed backup, and a trusted person who knows it exists) is usually sufficient.

The right time to set up multisig is before you need it. The wrong time is after a near-miss. If your stack has grown past the threshold where a single-seed failure mode keeps you up at night, start building the multisig in parallel with your single-sig wallet, move a small test amount first, and migrate gradually.

Sources & Citations
  1. BIP174 Partially Signed Bitcoin Transactions - github.com/bitcoin/bips
  2. Sparrow Wallet multisig documentation - sparrowwallet.com
  3. Unchained Capital vault service - unchained.com [VERIFY pricing]
  4. Casa collaborative custody - casa.io [VERIFY pricing]
  5. Coldcard Mk4 documentation - coldcard.com

Last updated 2026-04-14. Not financial or legal advice.

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