Touch ID is thought to allow securing iPhones and iPad tablets using a fingerprint, and one of its security measures requires the re-introduction of a security code after restarting a terminal, the fingerprint cannot be used. If you've ever wondered why iOS requires you to enter a security code after restarting, prohibiting the use of a fingerprint, well, the explanation is below. In practice, iOS does not store images of fingerprints in its secure enclave, but a mathematical representation of them, an image of the fingerprint that cannot be reproduced in its base.
Touch ID doesn't store any images of your fingerprint. It only stores a mathematical representation of your fingerprint. It isn't possible for your actual fingerprint image to be reverse-engineered from this mathematical representation. iPhone 5s also includes a new advanced security architecture called the Secure Enclave within the A7 chip, which was developed to protect passcode and fingerprint data.
The mathematical representation of the fingerprint is stored in a secure enclave that iOS can access, but not after a reset without entering a security code to unlock the terminal. To protect user data, Apple prohibits access to the secure enclave before the terminal is unlocked after restart using the security code set by the user. Although the data presented by Apple refers to the old A7 chip, nothing has changed regarding the security of fingerprints registered using the terminal reader, and now you know why we are forced to re-enter a security code after restarting.
