Fingerprint scanners are nothing new. They have been around for quite a while; being used on timeclocks for workforce management, and even at places like the gym for member check-in. This quick and unique method of identity has the potential to replace many other forms of plastic or paper identification, but should we be using it to unlock or lock our phones? Is there a security risk to having your fingerprint be registered and scanned by the phone you carry that could be lost or stolen? Are fingerprint scanners a serious risk to your privacy?
First, one would have to understand how biometrics work. Biometrics are methods of identification based on things like handwriting, facial structure, voice, eyes and fingerprints. Biometric systems are designed to not be reverse engineered. That is, a hacker would not be able to pull a list of results and use that information to break into accounts. While the paranoid might argue that fact, and argue that Apple is giving your fingerprints to the government (at least in the United States), the truth is that the technology doesn't support it.
To those parents worried about their teens getting fingerprinted before CCTV nabs them for shoplifting someday (hopefully never), consider how biometric systems register and store fingerprint information. The fingerprint scanner looks at your fingerprint and assigned a binary code to very specific regions of your fingerprint. No image is saved, just the binary code. Since every fingerprint is different, every binary code (which is generally encrypted) is different. Basically, a hacker could not build a fingerprint from a binary code as they would not know how that code is broken down to associate with your fingerprint since it is just a string of ones and zeros.
While Apple has loaded their fingerprint scanner with a host of helpful buzzwords about the resolution and physical properties, your fingerprint cannot be hacked. While some hackers have claimed to hack a fingerprint using household goods, they have hacked it from the outside, not from within the code. So you'd have to lose your phone and someone would have to care enough about its contents to attempt to replicate your fingerprint. So unless your teen is some sort of mega spy working for MI6 or the CIA, there is nothing to fear from fingerprint scanners on their cell phone.