Cold wallet for high-value self-custody
An Ownbit cold wallet turns a spare phone into an air-gapped signer for high-value holdings. The offline phone holds your key and signs by QR; an online watch-only wallet monitors balances and builds transactions. No dedicated hardware to buy.
Who is this for?
This is for anyone storing an amount they would be devastated to lose and who touches it rarely: long-term Bitcoin and crypto savings, a personal reserve, or the cold tier of a larger setup. If you already own a spare phone, you get hardware-wallet-style isolation without buying a device.
How do I set up a cold wallet?
Prepare two phones
Install Ownbit on both. Take one permanently offline — remove the SIM and delete saved Wi-Fi — to make it your cold wallet. Keep the other online as your watch wallet.
Create the cold wallet offline
On the offline phone, create a wallet, choose Cold Wallet (it unlocks once the phone is offline), pick a 12- or 24-word mnemonic, and back it up.
Pair the watch-only wallet
On the cold wallet, show the Set up Watch Wallet QR; scan it with the online phone to create a watch-only wallet that mirrors your addresses.
Send by QR
The watch wallet builds a transaction and shows a QR; the cold wallet scans and signs it offline; the watch wallet scans the signature back and broadcasts.
Full click-by-click steps with screenshots live in the guide: Set up a cold wallet.
Limits and trade-offs
- Every send needs two QR scans — deliberate friction that suits savings, not daily spending.
- The cold phone can't update over the network; updating means reinstalling online then re-importing the mnemonic offline.
- Large UTXO transactions can produce a QR too big to scan; lowering the amount or customizing UTXOs fixes it.
- It isn't strictly either/or with hardware wallets — for very high value, spreading single-key risk across a MultiSig is sounder than betting everything on one device.
Frequently asked questions
Do I need to buy a hardware wallet?
No. A spare phone kept permanently offline serves as the air-gapped signer. The security model page compares this with hardware wallets honestly, as trade-offs rather than one being absolutely better.
What if the QR code is too large to scan?
With UTXO coins (BTC, DOGE, LTC…) a transaction using many UTXOs can make the signing QR too big. Lowering the amount selects fewer UTXOs, or use Customize UTXO on the watch wallet to pick fewer.
Can I combine a cold wallet with MultiSig?
Yes. You can create a MultiSig cold wallet where the offline phone is one of the signers. See team and enterprise MultiSig for the multi-party side.
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Download Ownbit
Install the app, then set up a cold wallet or MultiSig for the workflow you need.