Cold storage

Cold storage means holding a wallet's private keys or seed phrase in a way that is never exposed to a networked device. The most common forms are hardware wallets (like Ledger, Trezor, Coldcard), paper wallets (a printed seed phrase or private key), and metal backups (a seed phrase engraved into steel or titanium plates for fire and water resistance).

The core threat model that cold storage defends against is remote compromise — malware, phishing, browser extensions, cloud sync leaks. If the private key never touches a device with network access, none of those attack vectors reach it. Signing a transaction with a hardware wallet still involves plugging the device into an online computer, but the private key material never leaves the secure element on the device; only the signed transaction does.

Cold storage does not defend against physical loss, forgotten passphrases, or supply-chain attacks on the device itself. The complementary discipline is recovery testing: at least once, restore the wallet from the seed phrase on a clean device, verify the addresses match, and confirm the backup actually works before you rely on it.