Having problems with Touch ID failing? Read this for help

Hi Joe,

It's been awhile since I've visited the forums on this topic. Thanks for continuing the fight. I have something very interesting to share. There's a technical podcast on the TWIT network called "Security Now" where the hosts touched on (see what I did there?!) a way to "overtrain" TouchID. Here's a link to the show — the relevant part starts at ~11:08

http://twit.tv/show/security-now/440

Essentially, you can continue to train TouchID beyond the initial session within the Settings app. Basically, go into Settings>General>Touch ID & Passcode, put in your passcode as prompted, and tap TouchID.

You should be able to see the registered fingerprints at the bottom of the screen.

Now, touch your finger to the sensor, and you will notice the respective listing for that finger briefly highlight through a shadow-flash. It's essentially registering a new sampling. This is much the same exercise as you described earlier in this thread except in a formal, controlled form. It's like a gym session for TouchID. I plan on giving it a go during edge cases like when it's cold or my fingers are dry in hopes of reducing non-responses.

I really think this is the key. Have a listen to the techie explanation if you are curious, as it does make sense. It's not just registering recognition of the finger — it is signaling new data added to the sampling.

<Edited by Host>

Joe:

You are definitely on to something with the pressure, and it makes perfect sense. As you note, the physiology of your finger does change the harder or softer you press down on it. It may explain why not everybody has a problem with TID, and why Apple has been slow to acknowledge a software issue, which may or may not exist (for one finger anyway...having multiple fingers enrolled does seem to cause some sort of failure).

After reading your latest post and suffering a bout of multiple "try again's" using my usual unlock method I experimented with the pressure of my thumb on the sensor. Waking the phone (by pressing the power button or home button) and then just lightly touching the sensor gives me an unlock every time, at least in the hour or so I've been playing with this approach.

My usual method was to depress the home button and let my finger rest on the sensor to unlock, which either worked very well or quite poorly depending on the state of my fingers (temperature, dampness, dryness, etc.). It occured to me after reading your post that I wasn't depressing (or nearly depressing) the button on registration. I therefore suspect the light touch works so much better because that is the way I initially registered the print, which seems to corroborate your findings.

Good job!

George Guerrero wrote:

Now, touch your finger to the sensor, and you will notice the respective listing for that finger briefly highlight through a shadow-flash. It's essentially registering a new sampling.

This did not work very well for me -- I only got the shadow-flash once in about every ten tries -- but I eventually noticed something about when it did flash that might help explain why some of us are having problems with the Touch ID & possibly a way to work around it.

What I noticed was that the home button sensor was not recognizing my thumb unless it covered all or almost all of the ring around the button.

From what I have gathered from various sources, the way the Touch ID device works is the ring injects a tiny amount of electrical charge into the flesh of the fingertip, & the sensor in the home button reads the electrical field pattern that creates. Fingerprint ridges & some other variations in the flesh of the fingertip create a more or less unique pattern. When that pattern is a close enough match to the one(s) stored in the phone during training, the phone unlocks.

So, with the realization that the sensor was not reading my thumb at all in "overtraining" mode unless most of it covered the ring, I think the root of the problem may be that just partially contacting the ring doesn't inject enough charge into the fingertips of those of us whose skin isn't very conductive for the sensor to get a good read.

With that in mind, I have started being careful to cover as much of the ring as possible with my thumb every time I try to unlock the phone. This seems to be working much better than anything else I have tried (which includes every tip mentioned here). So far, the phone unlocks on the first try almost immediately at least 90% of the time. It doesn't matter how hard I press, what the angle between my thumb & the button is, or how many different registration "slots" I have used for my thumb. All that seems to matter is how much of the ring I contact.

I hope this works for some of you as well as has for me.

Joe_Fo wrote:

Sorry, but that's false info. Plastic is an insulator. Cover your finger with a plastic bag, and TID will still unlock. See demo in the video for proof.

I'm not exactly sure what you mean by this. The ring is metal & does supply a charge to the finger, or at least that is what the patent filing info indicates. It is a capacitive sensing system, relying on the varying dielectric (non-conducting) properties of the finger to keep the charge from dissipating into current flow, just like in any other charged capacitor.

Also, I get a zero success rate unlocking the phone with my thumb covered with even a very thin plastic bag, & I'm now getting about a 90% rate if I am careful to contact all or almost all of the ring with my thumb.

Joe_Fo wrote:

Still not clear to me that complete ring coverage is required for the purpose you state ...

Neither am I. All I really know is I am getting much, much better & longer lasting results when I hold my thumb so that it covers as much of the ring as I can manage.

If I don't do that, the recognition rate quickly heads toward zero, even when I am careful to contact the sensor with the same lesser part of my thumb as I did when I first enrolled it, held at the same angle & with the same pressure.

About the only thing I am (relatively) sure of is that the sensor uses capacitive sensing methods to read the biometric signature of the fingertip, & that (as the Apple Doc you provided the link to very briefly mentions) that involves some "subepidermal" characteristics in addition to the fingerprint pattern itself. So despite what Apple says about the sapphire cover acting as a lens, I don't think any optical sensing methods are involved.

Joe_Fo wrote:

The only time I've had failures is when I've enrolled more than one finger for testing purposes ...

I have seen the same thing mentioned by a few others, but for me the number of fingers enrolled (including enrolling the same finger more than once) had made no noticeable difference. In every case, unless I'm careful to keep making sure I touch the sensor with as much of my finger as possible, the success rate gets progressively poorer with each Touch ID unlock attempt until eventually it doesn't work at all.

That's what makes this so frustrating -- what works great for some users doesn't make any difference for others.

BTW, I didn't mention it before, but both my wife & I have iPhone 5S models, both bought about three weeks ago at the same time from our local Apple Store, & set up with the help of store employees at that time. They are different colors but otherwise identical 16 GB models; however, their serial numbers are different enough that it seems likely they are from different production runs.

Both began having the same kind of fingerprint recognition problems around 24 hours after we got them home. For our two phones, it doesn't matter whose finger(s) are enrolled with either one.

Joe_Fo wrote:

I think you're missing the point. If you're having failures as you've described you need to both watch my YouTube video (link on first page) only enrolling one finger or thumb, and now I can add use firmer pressure during the enrollment procedure.

Try that before anything else.

Please believe me, I have tried everything you have suggested here, everything in your video (which I did watch carefully), the "overtraining" approach mentioned by George Guerrero (& watched the referenced TWIT video carefully too), & every other suggestion I could find.

That includes but is not limited to enrolling only one finger, enrolling one finger multiple times, using light or heavy pressure; plus restarting, resetting, or even restoring the iPhone for each new test.

But no matter what I try, if I am not careful to cover as much of the sensor as possible every time I try to unlock the phone, my success rate begins to decline & eventually goes to zero. Moreover, this is true for both our phones, using any combination of one of our phones & one (or more) of our fingers.

For our phones, it does not matter in the least if we enroll just one finger or several. Unless we are careful to cover the sensor during unlock attempts, each finger has its own limited lifespan, so to speak. IOW, if a thumb & say an index finger are enrolled, each of them works for a while & then does not, independently of the other digit.

That's what I meant about what works for some doesn't for others. If you wade through all the stuff on the web about this issue, that becomes evident -- just about every suggested method or technique has its share of successes, but there are also too many reported failures to dismiss them all as the result of not following the instructions carefully enough.

I started this thread and from day one, with two phones (and then 2 replacement phones), we, like RC-R (and others), have tried everything offered, multiple times (both me and my wife). Some limited success here and there, but ultimately frustration and levels of failure. I almost cringe each time a response comes in anymore because I know it is more guessing and trying, and hoping. I am very grateful for the many passionate folks who offer their inputs and desires to figure this out and help the mass market. However, I have grown weary and wonder if software brilliance will ever fix this someday from out of the universe. My wife no longer uses it and I keep hanging with it. I have an iPad Air and I have a sigh of relief each time I am required to enter my code and know there will be no 'Try Again' flashes of anger. I just had to vent one more time and share the many similar sentiments here in this thread and others. Thanks for listening to my emotional rant .