Definition
Air-gapped describes a device or environment kept separate from network-connected systems, without an active direct network link. In cryptocurrency custody, an air-gapped signing device can hold private keys and authorize transactions while an online device handles network communication. The term describes an isolation method, not a guarantee that hardware, software, or the information being transferred is trustworthy.
How It Works
An online system can prepare an unsigned transaction, which is passed to the isolated signer through a controlled channel such as a displayed QR code or removable storage. The signer reviews and signs it, and the signed result returns to an online system for broadcasting. The private key is intended to remain within the isolated environment. These transfer channels still carry data and require careful validation; an air gap does not mean that no information ever crosses the boundary.
Key Considerations
Isolation reduces some remote attack paths, but malicious firmware, physical access, contaminated media, and misleading transaction data remain relevant. Verify destinations and amounts on a trusted display and protect recovery material separately. Simply switching off Wi-Fi temporarily does not establish a well-managed air-gapped process. Updates and backups also need controlled procedures. Compare the complete security design and usability of a wallet rather than treating an air-gapped label as proof that it is safer than every connected hardware wallet.