"Wintergate" for Touch ID

Some days ago Pat Dryburgh wanted to coin the phrase "Wintergate" on his blog, ending the post with this paragraph:

"One hypothesis: people wear gloves during winter months. Good luck finding a pair with fingerprint projection technology."

First of all, I get the joke. But when reading it, I started thinking about winter and really cold weather – like frozen hand cold weather.

Despite the fact that wearing gloves is an issue for touch screens anyway and the iPhone doesn't like to operate in really cold weather conditions [Operating ambient temperature: 32° to 95° F (0° to 35° C) – taken from Apple's Technical Specifications page], I got curious about how Touch ID would work with really cold fingers.
I have to point out that I don't own an iPhone 5 yet, and if I did, I don't think I would conduct some scientific experiments to find out how cold your finger could get to activate Touch ID – even though it sounds really interesting.

Anyway, instead I read along about how the sensor works and when it recognises your finger, and this also got me thinking about the story of the disembodied finger to unlock the Touch ID sensor.
Mike Wehner sums it up perfectly on TUAW in my opinion:

"Based on what Apple has revealed regarding Touch ID and what the company's own patents have suggested, the sensor in the iPhone 5s utilizes two methods to sense and identify your fingerprint:

  • Capacitive -- A capacitive sensor is activated by the slight electrical charge running through your skin. We all have a small amount of electrical current running through our bodies, and capacitive technology utilizes that to sense touch. This is also the same technology used in the iPhone's touchscreen to detect input.
  • Radio frequency -- RF waves do not respond to the dead layer of skin on the outside of your finger -- the part that might be chapped or too dry to be read with much accuracy -- and instead reads only the living tissue underneath. This produces an extremely precise image of your print, and ensures that a severed finger is completely useless.

This means that the Touch ID sensor should be remarkably accurate for living creatures, but it also means that only a finger attached to a beating heart will be able to unlock it."

Coming back to the really cold winter situation, what happens when it's really cold outside and you don't happen to wear gloves, or you just finished doing something in the snow and your fingers are so cold that the outer layer of your finger appears to be frozen? Is the electrical charge still strong enough to activate the sensor, and is the "Image Generator" sensible enough to filter out your bad skin?

It'll be interesting to see if there will be any complications with Touch ID during this winter, and if Pat Dryburgh turns out to be the one who predicted "Wintergate".