OTP validator

The one-time password generated by the OTP authenticator is used for two-factor authentication. Traditionally, website login pages ask you to authenticate using something you recognize (your password). Two-factor authentication increases security while also requiring you to use your iPhone, or whatever device you're using, to generate a one-time password to verify your identity.

When you set up two-factor authentication, the website provides you with a secret that is stored securely in your iOS Keychain. When you log in using the authenticator, it uses that secret and the current time to generate a unique password. This time-based password proves to the website that the person trying to log in currently has the physical device containing the secret.

Syncing your secret token to another device disables functionality, opening the possibility for an attacker to steal your secret token without physical access to your phone. The same goes for cloud-based backups. To maintain the security of limiting tokens to physical devices, tokens follow the same backup rules as other passwords saved in the iOS keychain - they are only included in backups if the backup is encrypted.

To ensure your tokens are backed up, use iTunes to make an encrypted backup of your phone. Also, be sure to write down the "recovery code" provided by each website when you set up two-factor authentication and keep it in a safe place.