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A period of tape easily crack fingerprint recognition? This is not that simple

via:博客园     time:2018/2/11 17:31:09     readed:268

Text | Real Laboratory

A recent article that could crack the fingerprint of a mobile phone with a little bit of work is widely circulated online. Mentioned in the article, simply through the simple treatment, you can unlock the fingerprint on the phone, anyone's fingerprint, or even a napkin can be unlocked.


Although the conclusions of the article is very scary, but we carefully read through the presentation of the article process, we found that napkins crack mobile phone fingerprinting is not so dangerous, and even a little stupid in order to further authenticate our ideas, Buy a conductive ink pen, try to reproduce this experiment.


The shell is a bit crooked, but it's still a usable pen

The so-called fingerprint recognition "crack" principle

Why conductive ink can crack cell phone fingerprint recognition function? Before the formal experiment, real laboratory give you the answer to this question.

The vast majority of mobile phone fingerprint recognition are used capacitive fingerprint recognition technology, capacitive fingerprint recognition principle is the sensor and subcutaneous conductive electrolyte material to produce a small voltage, the size of the voltage by the fingerprint ridge ridges decision, the sensor according to the size of the voltage You can record the user's fingerprint information, and then fingerprint recognition by software algorithms.


Capacitive fingerprint recognition principle

However, due to the limited area of ​​the mobile phone fingerprint identification module, in order to improve the recognition speed, the fingerprint identification module will continuously record and learn the user's fingerprint information.

The above cracking method is to make the pattern of the conductive ink and the user correct fingerprint information superimposed to form a new fingerprint information, when the mobile phone recognition module identifies the user fingerprint information part is correct, it will give unlocked feedback and the overlap of conductive The pattern of the ink is also recorded as part of the user's fingerprinting changes. Then the next time the finger is unlocked with another finger or napkin, the conductive ink has acted as the correct fingerprinting information and can be fully unlocked with just pressing.

But is the truth true? The following immediately began to test!

Crack steps to reproduce

The principle is over, but this method can really crack the phone fingerprint? We buy equipment together to reproduce what.

The experimental procedure is very simple, we only need to prepare three things: a mobile phone with fingerprint recognition (we selected the iPhone 7), a roll of scotch tape, a conductive ink pen (is a creative tool for ink can be conductive , You can hand-painted circuit, the price is not cheap it).


1) First of all, we enter fingerprints into the handset and record only one finger. All the fingers except the finger can not be unlocked (here we record fingerprints on the left thumb).

2) Take a piece of scotch tape and draw a circle on the gummed side. We separately prepared 4 pieces of conductive patterns of different shapes and sizes of tape, and then one by one in the phone's fingerprint identification module glued to the test.


Dot conductive ink


Large dot conductive ink


Loop conductive ink


Two-point conductive ink


Posted on the phone fingerprint recognition module is like this

3) According to the news of the crack method, after affixing the tape, you also need to enter the finger fingerprint information to try to unlock the phone a few times. The result is that, even with conductive ink coverage, the finger that originally recorded the fingerprints can still be unlocked after trying several times, but the larger the conductive ink coverage area, the lower the probability that the originally entered fingerprint will be unlocked successfully.



Only painted dots and two-point conductive ink tape can be used to unlock the original entry

For the two patterns that can not be unlocked by the fingerprint already entered, we try repeatedly, after each failure, input the password to let the phone learn the new fingerprint feature, the result still can not be successfully unlocked, let alone cracked.

4) The point is coming, press the news of the crack method, then you should be able to use other fingers or napkins to unlock the fingerprint.

However, the result is not. Except for the fingers that were originally fingerprinted, the other fingers can not be unlocked. We use the second finger without fingerprinting multiple attempts, and all fail.



Even before the successful use of the original fingerprint to unlock the two patterns did not pass the second finger did not record the test fingerprinting

Next, we used a series of conductive inks and non-conductive napkins (representing conductive and non-conductive materials, respectively) in succession instead of trying to unlock the fingers. All the results ended in the following table:


To sum up, for this hand iPhone 7, to crack fingerprinting system this way, I am afraid not so simple, unless the machine just has a fault, otherwise the situation in the news is difficult to achieve. If this news is true, then it should be combined with other programs did not release the operation to crack fingerprint recognition, most people still difficult to reproduce this method of cracking.

After that we also tested the Nuts Pro 2 in the same way, which also ended in failure. I believe it would not be easy for other phones to move.

Even if this method can be easily reproduced, unless the original phone pasted "fingerprint"; otherwise the so-called cracked cell phone fingerprinting method completely does not work, the loophole is very large, but also very easy to be machine The Lord spotted, so Truth Labs thought the hole was not worth the worry.


The legendary fingerprint

However, to be on the safe side, it is recommended that you friends do not stick to the phone fingerprint stickers.

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