Understand fingerprint security

Secure location

• Capturing and recognizing your fingerprint must happen in a secure part of the hardware known as a Secure Biometrics Processor (SBP).
• Fingerprint data must be secured within sensor hardware or trusted memory so that images of your fingerprint aren't accessible.

Secure storage & removal

• Only the encrypted form of the fingerprint data can be stored on the file system, even if the file system itself is encrypted.
• Fingerprint data must be removed from the device when a user is removed.
• Rooting of a device must not compromise fingerprint data.

Google's guidelines require fingerprint templates—that is, the processed versions of raw fingerprint images—to be cryptographically authenticated.

Fingerprint templates must be signed with a private, device-specific key—like keyed-hash message authentication code (HMAC)—with at least the absolute file-system path, group, and finger ID, such that template files won't work on another device, or for anyone besides the person who set them up on the same device. For example, copying the fingerprint data from a different user on the same device, or from another device, must not work.

A device-specific encryption key—like Advanced Encryption Standard (AES)—must be used for fingerprint data so that a raw image or fingerprint template isn't readable by a separate device.