It isn't about just the printer, the thief also has to hold you down and take a 2400dpi picture of your finger.
That's what they used, but I don't think it was necessary. They did that to get a sharp 1200 DPI image.
Yet the Apple scanner is a standard 500 DPI sensor, which means it can only resolve a 250 DPI image (per the Nyquist theorem).
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The question is, what kind of thief are people talking about?
- If he's a grab and run type, then yeah, he'd have to hope that there's a latent print of your unlock finger somewhere on the phone that could be lifted, cleaned up, and sharpened with common photo tools.
- If he's got a gun and some control over you, he can just ask you to unlock it right there and/or to touch your unlock finger onto a piece of tape he slaps on the back of the phone before he takes it and leaves.
- If he's someone closer to the you, or has someone to follow you around, then there's all sort of opportunities to lift a print from something that you touched even before the phone was taken.
I think the conclusion that everyone is coming to, is that doing this to someone random isn't going to buy a common thief very much, at least as long as Apple doesn't allow the sensor to be used by apps or for shopping payments.
The worry is more about targeted victims. Rich. Famous. Government. Industrial. Military. Spouses. Business partners. Etc.
As I keep saying, it means you'd better trust whomever you fall asleep near, since only your finger is needed to unlock your phone. There's going to be a million TV shows with a female spy going through some sleeping guy's device.
If this demo turns out to be true, then it wouldn't be surprising if organizations put a ban on their employees enabling the fingerprint sensor. As I've said before, for real security, you want to use a combination of both the fingerprint reader AND a good passcode. Apple should put in such a mode.