Touch ID after a reboot

[Woochifer]

its even more annoying that u always have to enter the password the first time u try to buy somethin gat the appstore after a reboot like give me a break it already asked me to put it in after a reboot why ask for it again to purchase something. it makes the whole pay with touchid at the appstore redundant

Because after a reboot or any other power interruption, the decryption key for Touch ID gets purged. It's a security protocol that prevents someone from reverse engineering or otherwise intercepting the fingerprint data by taking the phone apart or hacking the hardware.

Touch ID is a feature that enables convenient security, but not so much convenience that it compromises the security.

Really, how often does the average user reboot their phone? This is a non-issue. If it's really that inconvenient to reenter a passcode, then you might be better off not having any security enabled at all. Over half of all smartphone users don't secure their phones at all, and I would guess that the inconvenience of it all fits in with what you're complaining about. However, keep in mind that over 80% of those with Touch ID-enabled iPhones do have the feature enabled. Touch ID is a feature for those who are choosing between some security versus no security. Those who want the higher security would choose a complex passcode.

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After rebooting why is it necessary to have to re-enter my password when I have Touch ID.

It can't be for security purposes because entering a four digit password is far less secure than using my fingerprint.

It actually IS for security purposes. Touch ID holds the decryption keys in memory, rather than in storage. When you reboot, the memory gets flushed. Keeping the fingerprint decryption keys in storage would leave it vulnerable to hacking if someone steals your phone. Here's what Apple's security white paper says.

How Touch ID unlocks iPhone 5s
On devices with an A7 processor, the Secure Enclave holds the cryptographic class keys for Data Protection. When a device locks, the keys for Data Protection class Complete are discarded, and files and keychain items in that class are inaccessible until the user unlocks the device by entering their passcode.

On iPhone 5s with Touch ID turned on, the keys are not discarded when the device locks; instead, they’re wrapped with a key that is given to the Touch ID subsystem. When a user attempts to unlock the device, if Touch ID recognizes the user’s fingerprint, it provides the key for unwrapping the Data Protection keys and the device is unlocked. This process provides additional protection by requiring the Data Protection and Touch ID subsystems to cooperate in order to unlock the device.

The decrypted class keys are only held in memory, so they’re lost if the device is rebooted. Additionally, as previously described, the Secure Enclave will discard the keys after 48 hours or 5 failed Touch ID recognition attempts.

 

[uhaas]

Police access

After rebooting why is it necessary to have to re-enter my password when I have Touch ID.

It can't be for security purposes because entering a four digit password is far less secure than using my fingerprint.

If you've followed the courts, you would be aware that the police can compel your fingerprint to unlock a phone, but not your passcode. If you shut it off, or if they keep it in evidence for more than the unlock without a passcode time, you're safe.

 

[Pagemakers]

With iOS 8 I find I am rebooting my phone every day or two due to it's instability.