The fingerprint scanner is actually a sensor that’s built into a stainless steel ring that surrounds the phone's home button. Users can store up to five fingerprints on a supported Touch ID device. Verified users can then unlock the device or authorize purchases from Apple's iTunes Store, App Store or iBooks Store by pressing the device's home button. Other apps cannot access the fingerprint data, which is encrypted and stored on the device's processor.
At the time of its release, critiques warned that Apple Touch ID by itself is not a security feature because it is too easy to gain access to a device by using fingerprints left on other surfaces. Proponents of the technology believe that Apple Touch ID is still useful because fingerprints are more secure than weak passwords.
Touch ID, which debuted on the iPhone 5s in September 2013, is expected to be used on other Apple devices in the future. The technology was first developed by AuthenTec, a biometric security vendor that Apple acquired in July 2012.
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