The Bitcoin Computer is a clean machine that goes online carefully. This is the next rung: a computer that cannot go online at all, because the hardware to do so has been physically removed. Whatever is on it stays on it. That makes it the most capable tool in deep cold storage: a full keyboard and screen for dice seed work, offline signing, and encrypted records, with no radio to betray you.
Kill the Radios First
Air-gapped means physically unable, not "WiFi turned off." Open the machine and remove the WiFi, Bluetooth, and mobile-broadband cards outright, and disable or avoid Ethernet. Three good starting points:
- An older ThinkPad (the X230 is the community classic): cheap used, easy to open, wireless modules unplug in minutes, and it is friendly to Libreboot if you want open firmware underneath.
- A Raspberry Pi Zero 1.3: ships with no WiFi or Bluetooth at all, nothing to remove. Command-line comfort required.
- A desktop built without any network hardware in the first place.
Install Everything Offline
Prepare on another machine, install on this one. Download and verify a Linux image (Mint is a comfortable pick), write it to USB, and install with LUKS full disk encryption from the start. Then bring over the tools the same way, verified first: Sparrow or Electrum for PSBT work, and an offline BIP39 tool for seed math. From the first boot onward, nothing goes onto the machine except through deliberate, verified transfers.
How Transactions Cross the Gap
The workflow is the same PSBT dance as any air-gapped signer. Your online coordinator builds the unsigned transaction; it crosses to the offline machine as a QR code or a microSD card; the offline wallet signs it; the signed result crosses back and gets broadcast. Prefer QR when you can, since a camera cannot carry malware the way removable media theoretically can, and treat any USB stick that has touched another computer with suspicion. Keys never cross in either direction.
This or a SeedSigner?
Both are air-gapped; they serve different temperaments. A SeedSigner is stateless, single-purpose, and simple: it signs, and it forgets. The air-gapped computer holds encrypted state and does more: it can store encrypted backups and inheritance notes, run seed tools with a real keyboard and screen, verify addresses at length, and look like an ordinary laptop on a shelf rather than recognizable Bitcoin gear. It also demands more discipline, which is the price of the versatility. Plenty of people run both: SeedSigner for routine signing, the air-gapped machine for ceremonies.
⚠️ This is deep cold storage, not a daily wallet. The setup is slow on purpose, and the discipline is the security: the machine never touches a network, media crosses the gap only when verified, and the seed still rules everything. Anyone with your seed owns your coins, air gap or not, so the backup rules apply in full.
Go deeper. Put open firmware under it with Libreboot or Coreboot, generate seeds with your own dice, or compare notes at a meetup.