The offline private key can also function as a token in two-factor authentication.
The idea is that a digital key to decrypt and recover sensitive or personal data should have long-term durability and not be stored on any computer or network.
Early implementations of a paper key by the company Safeberg use a Data Matrix barcode.
[2] The user stores the printed key in a secure location.
To avoid abuse, the key can only be used in combination with a ‘normal’ password.