Wednesday, 11 September 2013

You are the Key: Fingerprint Scanning on the iPhone 5S

So, here we are. Another iPhone launch and seemingly even less features. The September 10th launch of the iPhone 5S brings the only physical feature of note: fingerprint scanning via “Touch ID” which is built into the main button of the phone (an elegant way of doing it by the way). This turn of events is more about a push by Apple towards acceptable secure m-payments and stronger user authentication for the web and app store rather than just being completely about access control to the device itself. I’m pretty sure that there’s a strong pull from the business / enterprise sector as well for this kind of technology. In my experience, senior management seem to quite like things they’ve seen in a sci-fi film such as palm-print security access and voice recognition in front of big strong-room doors. Perhaps a blue LED or two to top it off. That of course, is real security. Not.

Just like in the movies! It must be secure!

 So what does this technology really bring us and why hasn’t it been implemented before? Let’s concentrate on just the access control piece here.

Leaving your keys hanging around

Unlike PIN numbers, you leave a number of exact replicas of your fingerprints in various public places when you go about your daily business. That’s like leaving an exact imprint of your front door key over twenty times a day on things like the side of your car door, on a coffee cup and on the table of your favourite pub. In all likelihood, the back of your mobile phone probably contains a pretty good copy of your fingerprint right now. In 2008, the German interior minister Wolfgang Schauble found this out when hacktivists collected his fingerprints from a glass. And remember: once you’ve lost your fingerprint you can’t really get it back (you only have a limited number!).

There are some pretty extreme examples of people who’ve been tortured for bank PIN numbers and even one case in Malaysia where a man had his finger cut off to steal his fingerprint protected Mercedes.

There is an argument to say that most street thieves (like burglars) are not going to want a direct confrontation with the owner, but there’s also plenty of evidence of violence during mobile phone theft from people being shot or held at knifepoint, just for their phone. 

One could easily imagine a scenario where the user is just forced to open up the device and remove the security protection before the criminal makes off. This scenario could just as easily be argued for users with PIN protection and it seems (from my unscientific hearsay point-of-view!) that we haven’t heard of many instances of thieves doing this. What seems to be more prevalent is either unattended theft or snatch theft where the phone is actually being used (and is therefore unlocked and ready to go).

"The number of phones found on the London Underground alone was 25,000 in 2011"

According to the Office of National Statistics’ report on Mobile Phone Theft [pdf], the Crime Survey of England and Wales for 2011/12 showed that 7 in 10 incidents of mobile phone theft were personal thefts (e.g. pickpocketing or snatch) or ‘other thefts of personal property’. These ‘others’ are defined as:

“items stolen while away from home, but not carried on the person (such as theft of unattended property in pubs, restaurants, entertainment venues, workplaces etc.).”

Let’s also bear in mind that a lot of people could believe they’ve been pickpocketed or that their phone was stolen from somewhere when they have in fact just lost their device. The number of phones found on the London underground alone was 25,000 in 2011.


What fingerprint biometric technology does give you is convenience, more so given that the sensor for Touch ID is built into the key that you would have to press anyway. Instead of having to make four or more finger movements and the possible engagement of brain to remember a PIN, you instead have almost instantaneous access, which when you consider how many times you have to enter your PIN into your phone every day is surely a good thing. What convenience then hopefully gives you is increased adoption by users, which overall is again a good thing. Most people using fingerprint access control security than a few using a PIN is a much better situation for everyone.

However, this is certainly not all a bed of roses. Usability is a big issue once you look into it (and I’m not sure how much Apple have taken this into consideration).

Some people just simply can’t use fingerprint readers. For example, the very young, the elderly and some disabled people. In addition “False negatives” can be caused by various factors such as:
  • Long fingernails
  • Arthritis
  • Circulation problems
  • People wearing hand cream
  • People who’ve just eaten greasy foods
  • Fingerprint abrasion, includes: the elderly, manual labourers, typists, musicians
  • People with cuts

In some senses, this functionality could be regarded as socially regressive, or at least a not socially inclusive and accessible technology. These types of users must fall back to things like PIN usage to provide access control.

Technology progression

Technical details of the Apple solution are not clear, but a lot of fingerprint technologies have failed in the past and I am sure that this one will come under intense scrutiny by security researchers. I have demonstrated the “gummy finger” attack against an optical fingerprint scanner myself at conferences and in lectures, even creating a working latex ‘replacement’ fingerprint ala ‘Diamonds are Forever’.

Researchers have even gone as far as ‘lifting’ fingerprints, reversing the image (to get it back to the right way round) and etching them in order to create a pattern for new, usable replicas (see the gummy finger link above for more details). Other researchers have also defeated ‘liveness’ or pulse detection too.


So what do I really think? I think for high-end enterprise use cases (one area that Apple has been really going after in the past couple of years), this does make sense. I can imagine a CEO complying with that kind of policy more than a mandatory very long PIN or password. If they’re really important people though, you can certainly imagine them being targeted to copy their fingerprints as I mentioned at the beginning.

For your average user, maybe just maybe, the convenience aspect will make this a success. What that would mean is more devices secured at rest (i.e. left on café tables), so an opportunistic thief would not be able to get immediate access. It could even provide a different, potentially more secure way of authenticating to banking and payment services over the web or in a shop. I truly hope that users do not become the targets of more violent assaults where they are forced to give fingerprint access to their device.

Lastly, I hope that the Apple security engineering team have done their job correctly. At the end of the day, your fingerprint is translated into 1s and 0s. A representation of this has to be stored on the device in some way. Each time you access your phone, your data is then processed through an algorithm to get compared. If that is not done properly using secure hardware, then there’ll be another set of people producing hacking tools to address a new market for criminals to get around the fingerprint protection. The first commercially sold fingerprint scanner on a phone that I remember was in 2004 in the GI100,a PanTech device that was released in Asia. I looked into and rejected fingerprint scanning as a possibility for mobile phones at Panasonic in 2005 for many reasons (not least the processing capability needed). Nearly 10 years later it’ll be interesting to see whether it really is a useful security technology or just simply a movie-inspired gimmick.

1 comment:

  1. Thanks for the comment - my feeling is that whilst most security researchers have backed away from fingerprint scanners for a while, there'll be a resurgence in interest. Of course, I hope the technology holds because it opens up exciting areas for users and the security world. Processing power is much better than it was too. The human element will always be the difficult issue!


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