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Paper Keys

The Design Problem

When wanting to grant access to a resource in a decentralized system, we can’t necessarily depend on a trusted single central controller. Instead, we use cryptographicly-secure secret passwords, or “keys,” that grant access to resources. A reosurce could be an account, a group invitation, or a piece of data.

These cryptographically-secure keys can be very large, sometimes hundreds of characters. Because of this, it can be difficult to save or share these keys in the physical world.

The Design Solution

The user can save or print a file that can be used to gain access to the resource. The file itself should be easily human readable and printable.

You can use this in conjunction with the QR Code verification pattern to make it easier to import the codes with the device’s camera.

Examples

  • Disk encryption recovery keys (Apple)
  • 2FA backup codes, (GitHub, Lastpass)
  • Keybase
  • Delta Chat burner account codes.

Why Choose Paper Keys?

Paper Keys is a safe and accessible method to verify, share, or backup information.

Best Practice: How to Implement Paper Keys

It is advisable that users know the risks, and have a secure and oragnised place to store the keys. Be clear with users that they should print it or save it in a safe backup location in case their device gets lost or stolen.

Potential Problems with Paper Keys

If lost, access to data is potentially lost permanently.

If found by an adversary, it can lead to unauthorized access to data.

The Take-Away

References & Where to Learn More

Projects by IF has outlined a similar design pattern called Recovery Codes.