The Chaos Computer Club reports that they have successfully made a fingerprint that fools the iPhone 5s scanner using nothing more than a high-resolution photo and a painstaking but not-incredibly-hard arts-and-crafts process. This is the least surprising thing in the entire world, but since I was just talking about the fingerprint scanner in my last post, I thought I’d follow up.
So basically, as real security goes, fingerprints are a terrible, terrible, terrible security measure. You leave them all over the place! Hilariously, as various people have noted, you specifically leave high quality fingerprints on the glass of your smartphone. Fingerprints are probably the worst biometric measure for security, and honestly biometrics are pretty bad for security in any case. Extensive testing for the last few decades have demonstrated pretty conclusively that it’s always fairly easy to create fake whatevers, be it faces, retinas, etc., that are good enough to fool biometric scanners.
And biometrics have a uniquely terrible security property, which is that you know what you’re looking for. With a password/passphrase, there is at least the chance that the target of your attack has done something like generate a truly random password, or otherwise made a difficult choice for you to attack. But if you’re looking at a fingerprint scanner, your path is obvious: get their fingerprints. Which they leave lying around everywhere. Nobody’s fingerprints are any more secure than anybody else’s fingerprints. At least, not without heroic measures like wearing gloves literally everywhere.
And of course once one of your biometric measures is compromised, it’s compromised forever. You aren’t changing your retinal pattern just because someone stole the files from your optometrist’s office.
This is… I was going to say that this is an “open secret,” but honestly that overstates the secrecy of the weakness of biometrics. Everybody who cares has known how bad biometrics are for security for years and years.
That all being said, why did I give a qualified endorsement of the 5s fingerprint scanner?
Well, you know what’s even worse security than a fingerprint scanner? No security at all. Which is how much security I have on my smartphone, because who wants to type in a PIN every time they unlock their phone? And incidentally, possibly the only thing that may be less secure than a fingerprint scanner is a 4 digit PIN (well, arguably. There are ways in which the PIN is more secure). And the fact of the matter is that if you’re getting your security advice from Sandor at the Zoo, you probably don’t have really deep security needs. It might only take a half hour of arts-and-crafts to fake your fingerprint, but if that’s more time than anyone’s willing to invest in attacking your smartphone, you’re still good.
So basically: the security provided by a fingerprint scanner is flimsy as hell, but it’s better than nothing, and by all reports, the 5s scanner is a very slick way to unlock your phone that is marginally better than no security at all. Thus: endorsed. As long as your security needs are light.