The traditional 1Password security model includes an account password and a Secret Key for authentication. You can also choose to authenticate with a passkey. When you set up a recovery code, you create an alternate way to access your 1Password account without any of those elements.
Technical design
When you sign in to 1Password, your credentials either derive or wrap a 256-bit encryption key that grants access to your account. A recovery code, which is also a 256-bit key, derives a second encryption key. This second key is used to encrypt the same intermediary key that’s typically encrypted with, and only accessible by, your account credentials.
Both your recovery code and identity verification are necessary to regain access to your account. Each element plays a different role, and they work together to make sure your recovery code alone can’t be used to take over your account.
The recovery code is cryptographic, and allows you to decrypt and regain access to your 1Password account. It’s your responsibility to protect your recovery code and store it securely.
Identity verification allows you (and only you) to use your recovery code. You verify your identity with access to your email account, while 1Password servers are responsible for the verification process.
Security model
Recovery codes allow you to access your 1Password account without the two-secret key derivation (2SKD) 1Password uses to derive two independent keys during a traditional sign-in process. While 2SKD requires your account password and Secret Key, recovery codes divide your account access into two distinct parts: a cryptographic step and an identity verification step.
When you start the account recovery process, 1Password uses an authentication subkey of the recovery code to prove your identity through SRP. This sets up an encrypted connection to our servers, similar to a traditional sign-in process. After you prove your identity with email verification, our servers transmit information to you, and 1Password decrypts it with a different subkey of the recovery code.
Security considerations
A recovery code is a great alternative to your Emergency Kit, because it alone can’t be used to access your 1Password account — you still have to verify your identity. Adding identity verification to knowledge factors is designed to make it easier to balance security and usability in an emergency situation.
Additionally, 1Password servers can protect the use of recovery codes. For example, you must be signed out of your account and not have accessed it recently to use a recovery code successfully. These requirements can’t be enforced when you sign in with your credentials or someone else signs in with a copy of them, because the two processes are indistinguishable from each other.
When we designed recovery codes, we prioritized access for the user who has the ability to sign in to the account with their credentials rather than someone using only the recovery code. This intentional decision makes it difficult for a recovery code to be used as an account-takeover tool.