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An orange peel will unlock your phone.

via:中国科普博览     time:2019/8/13 10:57:35     readed:43

Some time ago, the orange peel was unlocked on the Internet.Mobile phoneEvent:

Transparent tape paper, conductive pen, orange peel, toilet paper, these seemingly impossible things together, why can they play the role of replacing fingerprint unlocking?

Is it hard not to find a unique fingerprint that corresponds to an equally unique vein in the orange peel?

Or is orange peel really spermatogenic?

No, no, no.~~

In fact, the truth is that ---------- (look down)

At present, our commonly used method of mobile phone unlocking is capacitive mobile phone fingerprint unlocking. Simple and fast unlocking features are popular with consumers, so it is also the most widely used and mature fingerprint unlocking method.

The condition for judging whether your mobile phone is capacitive fingerprint unlocking is whether there is a metal ring near the unlock key. With this metal ring, when the finger is close to the unlock key, it will wake up the fingerprint recognition function of the mobile phone. As shown in the following figure:

How can we not tell the truth before uncovering the phenomenon? So, we must know: how does the fingerprint unlock key of capacitive mobile phone work?

In fact, this small button is composed of capacitive pattern recognition modules which are formed by silicon crystal elements and electrolyte, that is, some small sensors. The sensor is connected to a small capacitive plate, and the capacitance value in these small capacitors depends only on the distance between the plate on the sensor and the fingerprint surface, as shown in the D in the figure below.

In the formula, C is the capacitance value of the capacitor. Vacuum dielectric constant is equal to 1, K is the constant of electrostatic force, S is the area facing the two plates, D is the distance between the two plates. As the name implies, capacitance is a device that can store electricity, and the larger d, the smaller capacitance, and vice versa. When the capacitor discharges at a constant speed after charging a certain voltage, the smaller the capacitance or resistance value, the smaller the time constant, and the faster the charging and discharging speed of the capacitor.

As we all know, the fingerprints of human fingers are clearly and uniquely lined by thin ridges like mountains. Ridges have grooves, and these subtle differences in height make fingerprints feel uneven and scattered.

When you press the unlock key, the capacitance on the ridge of fingerprint is large because of the small distance, and the capacitance on the ditch of fingerprint is small because of the large distance.

At this point, the sensor will charge all capacitors, and when the capacitor is charged to a certain voltage, it will start discharging. Because the capacitance under the ridge is high, the discharge is slow, while the capacitance under the ditch is low, so the discharge is fast.

By detecting different discharge rates at different capacitors and converting them into an 8-bit output, a very good original fingerprint image can be formed. Store it in your cell phone, and it will form the default "key" for your cell phone to turn on.

When you try to unlock, the algorithm in the mobile phone will select a number of points on the fingerprint (generally more than 30) for calculation and comparison. If your fingerprint matches the fingerprint set in your cell phone, you and your cell phone will be able to "code" successfully, and you can start playing.

But why can orange peel also be the unlocking tool for your mobile phone?

In fact, there is a very important thing in these tools, which is the conducting pen.

Because the conductive coating drawn by the conductive pen can also form capacitance with the button, when the unlock key is covered with transparent tape paper painted by the conductive pen, and you unlock it three times with your fingerprint, the mobile phone will learn the new unlock pattern. This new pattern contains not only some fingerprint information of your finger, but also information of conductive coating.

At this time, not only orange peel, but also other people's fingers, wet paper towels... All of this can unlock your cell phone and squander your money.

But why can mobile phones learn the patterns of conductive coatings? It's not like fingerprints!

This is because of the bug in the algorithm of the general fingerprint recognition system of mobile phone. Fingerprint recognition algorithm can only identify patterns, but can not identify whether it is a fingerprint of living skin. althoughAppleSince the launch of the mobile phone, it has claimed that the use of radio frequency technology to detect whether it is dermis. But the reality of its application is very bleak, it is still okay as long as the pattern is right.

Speaking of fingerprint unlocking, mobile phone fingerprint unlocking is so convenient now. Do you remember when it was born?

On September 10, 2013, Jobs released his latest mobile phone.——IPhone5S. This mobile phone is an innovative application of Apple's patented "wireless matching and communication system between devices using biological features", translated into vernacular, which is a technology to encrypt and control or apply for access to electronic devices using human-specific properties, such as fingerprints, iris, voice, face recognition, etc.

Since then, the development of mobile phones has undergone tremendous changes. The world's major mobile phone manufacturers follow up quickly, including HTC,SamsungAll of them started to study fingerprint unlocking technology, and quickly released mobile phones with related functions.

Until now, after a few years of development, the use of biological features to unlock and encrypt mobile phones has become one of the essential functions of all smart devices. We have to lament that the development of science and technology makes our life more diversified and more convenient.

Now, orange peel can also achieve fingerprint unlocking, are the little friends panicked again???

That's not necessary, because——

If your mobile phone stays with you for 24 hours, who can take your mobile phone to make small actions beforehand?

There's another reason you don't have to panic. It's——

Not all fingerprint recognition devices use capacitive sensors, but also optical and bio-radio frequency sensors.

Optical fingerprint identification equipment

Optical fingerprint recognition is an early fingerprint recognition technology. Light is reflected back to the machine to get data. This way is to collect finger feature points, which is different from the principle of mobile phone module. However, the same thing with the mobile phone module is that it can not identify whether it is dermal skin fingerprints. Moreover, this kind of equipment is generally larger... At present, the common application is: the company's fingerprint puncher.

生物射频式或超声波生物射频指纹识别设备

Bioradio Frequency or Ultrasound Bioradio Frequency Fingerprint Identification Equipment

This technique uses radio frequency signals to obtain fingerprint images. Ultrasound equipment emits ultrasound waves to the surface of the finger and then receives the reflected echoes. This radio frequency signal can penetrate the surface of the finger, so it can not only detect fingerprint lines, but also identify whether the fingerprint is a dermal skin fingerprint. Although this technology is more effective for fingerprint identification, it is still not mature.... At present, the common application is fingerprint collector of public security system.

Now, what we're waiting for is a reliable technology and computing algorithm for mobile phone applications that can not only quickly identify fingerprints, but also accurately detect whether they are dermal skin or not.~~

Look at you guys, buddies.

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