If fingerprints are unique (research suggests they are) then why doesn't my phone tell me this finger is already added if I add the same finger twice? On all of my fingerprint id phones I can add my fingers each twice or more. Some early fingerprint sensor discussion of the version 1 phones suggest this improves the finger sensor success rate. But the sensor has improved, so why does it still allow you to add the same finger twice?
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Other Why can I add the same fingerprint twice or more?
- Thread starter InnSuu
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It allows several different finger prints.
It isn’t smart enough to compare them. That feature wasn’t programmed into it.
It isn’t smart enough to compare them. That feature wasn’t programmed into it.
Not sure why it does this without warning but I do my index fingers or thumbs twice. Depending on phone layout. As it decreases error rate. By making sure my entire fingerprint is covered. As sometimes I use the edge of finger to unlock. Depending how I'm holding the phone.
If you try to add a fingerprint again, why should it tell you, you already registered that finger?
Because after adding the same finger 3 times or even 300 times there comes a point you begin to question this security feature.
Since the replies here I found interesting articles on the uniqueness (or lack of) in fingerprints, how fingerprints are used to create algorithms to use on phone finger sensors, and some miscarriages of justice due to flaws in fingerprint research.
This is a very interesting observation. I wonder how much time it will take for Apple to improve the fingerprint analysis algorithm so that the phone is capable of identifying when a finger is registered again. One factor might be how much of the same portion of the finger was used from one reading to another (at least). With the capability of the processors now incorporated into these phones, it seems like this should be achievable.
For me, TouchID works around 60% of the time due to working with my hands for over 25 years. I used to register my thumb three times and my index finger twice to cut down on failures and it helped a lot. FaceID was a main reason for me buying the iPhone X when it was released and has been a welcome change. It has made a huge improvement in my iPhone experience and I have no interest in owning another TouchID device
I remember when the iPhone 5s came out and some of them had better Touch ID than others and the trick was scan the same finger multiple times so it worked better. I think they worked it out for the iPhone 6.
I agree with this. I also like the feature - On my 8 Plus (and I would assume all other iPhones with fingerprint sensors), 5 fingerprints can be registered. One fingerprint registered 5 times means greater accuracy, and no room for an unauthorized person to "sneak" their fingerprint onto your device.
Nevertheless, I like the facial recognition on the 13 more.
iPhone 6 had the same sensor as the 5S. The 6S had the 2nd Gen TouchID sensor that is still used on the new SE3..
You are right about the 6 and the 5s being the same sensors but I think they improved reliability. The 6s introduced the second generation Touch ID that is still being used.
My question is how will an unauthorized person sneak their fingerprint in? That assumes they have access to an unlocked phone, and at that point, whatever type of security was on there is irrelevant
They can't. To even get to the setting to add a fingerprint requires at least a password (if memory serves me correctly). So they would have to get access to the phone (without the owner knowing) while it was open at the 'add fingerprint' screen.
Why would I question it? It’s not recognizing new fingerprints. One scan isn’t any more or less secure and is likely even using most of the same points for verification. The only complaint may be the idea of diminishing returns with added effort. Plus, you can’t add 300 fingers if my memory serves. Isn’t it like 5 or so?
Much to do about nothing. Fingerprints are unique. The quality of the algorithms and methods of identifying one from another may be more or less accurate but you are REALLY thinking too hard about this.
Apple had a stat that said 1:1,000,000 or something like that. Which means - In theory - it could falsely recognize you. However, that is well beyond the “reasonable doubt” standard.
In terms of miscarriage of justice - I would suspect most of the miscarriages would be a result of mis-assumptions based on fingerprint evidence (like his fingerprint is on the door so he must have killed her). But I didn’t read your articles ?♂️
Interesting question but I’ve always appreciated the fact I could add the same finger twice. No idea how anyone could claim that’s a bad thing.
You're right, I guess I was just "thinking out loud" in my post . . . .
Because the phone doesn’t compare the finger prints. Duh. If you want to speed up the scanning, open the Touch ID settings and train it by resting your finger on the Home Button until that finger „entry“ is greyed out, lift the finger and repeat the process.
It's not a question of why the phone doesn't compare the fingerprints. The question is, how come the phone doesn't know that that finger has already been added.
The answer is to do with the fact that fingerprints are actually not entirely unique. Apple use your multiple fingerprint touches during setup to work out a unique algorithm based on those multiple touches. So adding a finger twice just initiates the process again. Adding the same finger twice or more increases the chance of the fingerprint sensor working on that specific finger, but it reduces the security by diluting the algorithm.
Because Apple never implemented such a mechanism, they just didn’t bother because there’s no need.
Also Apple never claimed it was entirely perfect or completely unique, mentioning an estimated that a the chance of someone having the same print as you is 1/50000.
You're picking up something I never put down. I do not claim to know what Apple 'bothered' to add or not. I merely mulled the process and how it is implemented. I am very interested in the uniqueness of fingerprints. Your numbers for fingerprint uniqueness, did you get those from Apple?
As I said, Apple stated it so yes, I got this from Apple.
Your question was why you can add the same print multiple times, and the answer is because Apple doesn’t care if you do or not. Case closed, I’m not picking up anything from you.
Can you link to an "Apple does not care if you add one or more fingerprints..." article?