There are three main types of fingerprint scanners: optical, semiconductor, and ultrasonic. Although mobile devices were the first to use semiconductor sensors, we will start with optical scanners, which came earlier.
Optical scanners, in turn, also come in three types: those that measure residual light, those that measure reflected light, and non-contact sensors. The first type of scanner requires external illumination and measures the amount of light that has passed through the finger in the grooves and protrusions – as you might guess, such a scanner will see the grooves as brighter places. Translucent optical scanners were not used in mobile devices.
The second two types of optical scanners are similar in that they have an internal illumination source. The difference is that scanners that measure reflected light “see” only the grooves of the finger, since they fit snugly on the glass, while non-contact scanners, in fact, create a complete photograph of the print, and only then compare it with the standard.
Unfortunately, it is almost impossible to find information about what type of optical scanner is used in a particular gadget, but, in general, the championship of the first mobile phone with an optical sensor belongs to the aforementioned Pantech GI100.
Since then, attempts to introduce optical scanners into smartphones have been repeated several times – the first Android smartphone with such a sensor (and a fingerprint sensor in general) was the Motorola Atrix 4G.
Optical sensors are quite simple in design, but they have a number of disadvantages, including low protection against dummies. But the main reason for the rejection of such scanners in smartphones was their large dimensions (even despite the use of roller and broaching mechanisms), because they require a full-fledged optical sensor and backlight.
So far, this type of sensor is not widespread, but everything indicates that it is the future behind it. Firstly, as the name implies, such scanners use ultrasonic waves, which leads to the absence of the need to use a separate platform for the sensor – it can be built anywhere, even under the display.
Secondly, the frequency of sound in such scanners is tuned to reflect waves from the human body, which means that it is still impossible to deceive such a sensor by mechanical means – such methods have not yet been found. And, thirdly, it is ultrasonic sensors that are able to scan prints at maximum resolution and even create their three-dimensional models – they have no equal in terms of accuracy and response speed.
Ultrasonic sensors for use in smartphones are being developed by Qualcomm, which has named its technology Sense ID. The Chinese LeTV Le Max Pro smartphone was the first to receive an ultrasound scanner, and they can also be found in the Sony Xperia Z5 flagship line. According to rumors, several smartphones from different companies with such sensors are being prepared for release at once.
The essence of the sensor
By the words “fingerprint sensor” we mean a small scanner that recognizes the pattern on the skin of the finger applied to it. Previously, such a sensor was too expensive, and therefore it was used only in banks, as well as in some government and military institutions. And the dimensions of the scanner were too large, because of which none of the smartphone manufacturers even thought about its implementation.
First of all, the fingerprint sensor is designed to protect the contents of the smartphone from prying eyes. If another person picks up your device, then they will not be able to go beyond the lock screen. The fingerprint of any of his fingers will be different, and therefore he will not be able to unlock the device. In theory, the scanner can be fooled. But this is such a laborious process that only special services can cope with it, and even then not always.
Also, such a sensor is used in ensuring the security of payments. If earlier a password was entered to confirm the payment, now it is not necessary to remember it – just put your finger on the scanner. It is very comfortable! In the same Play Market, people do not turn on payment confirmation with a password, as they simply forget it.
Semiconductor sensors use the property of semiconductor materials to change their characteristics under external influence – temperature, physical, electrical. The first pocket gadget with such a fingerprint scanner was the HP iPAQ 5550 PDA. It used a temperature sensor that responded to the temperature difference between the papillary pattern tightly adjacent to the scanner and the sensor itself.
Two more types of semiconductor scanners, radio frequency and pressure sensitive, are quite rare and have not yet been used in mobile gadgets. RF sensors emit a weak radio signal, which is reflected from the papillary pattern and enters the sensitive matrix. It is almost impossible to deceive such a sensor, but if the finger contacts the scanner poorly, its operation will be unstable.
Capacitive sensors have gained real popularity in smartphones, and not without the help of Apple. Despite the fact that there were fingerprint scanners in smartphones before, the Apple company was the first to realize a compact and fast sensor, which, moreover, would have a convenient location.
The principle of operation of such scanners is similar to the principle of operation of capacitive touch displays: human fingers conduct an electric current, which changes the charge of the sensor’s microscopic capacitors. Moreover, the papillary pattern changes the charge more than the grooves, which allows you to get a clear image of the print.
Quite often, capacitive sensors in modern smartphones are called optical, but this is fundamentally wrong. Although capacitive scanners, like optical scanners, use CMOS sensors for signal processing and capacitors to measure the difference in sensor exposure between grooves and ridges, capacitive sensors do not contain photodiodes and do not need illumination, which makes them smaller and faster. .
Of course, like any new technology, the fingerprint scanner has a number of disadvantages.
Secure storage of fingerprints
Currently, the main function of fingerprint sensors in smartphones is security. Moreover, in absolutely all devices, fingerprints are used only as an addition to the password, which you still need to enter in case of recognition errors, after rebooting the gadget, and in some other situations.
Despite this, if you can set any password, then the fingerprint is unique, and falling into the wrong hands can turn into a nuisance. This makes it necessary to apply special protection methods for fingerprint images. The first feature of these methods is the use of a special secure chip or a separate area in the chipset to store information about fingerprints. Different companies have given this technology their names: TrustZone (ARM), Secure Enclave (Apple) and Snapdragon Mobile Security (Qualcomm).
having the original, you can say for sure whether it matches the reference hash sum, but if you have only the hash sum, then it is impossible to restore the original from it. In addition, to increase the speed of sensor response, the possibility of recognizing a print at an angle or even in part of a print, not a complete comparison of prints is used, but according to the so-called “details”.
To some people, the above disadvantages may seem far-fetched. But actually it is not. Although no one will argue with the fact that smartphones with a fingerprint scanner have more advantages. It’s not for nothing that Google has implemented support for a fingerprint sensor at the deepest level in its operating system. It is possible that even the cheapest smartphones will be equipped with them in the future.
In the meantime, be sure to read the reviews for the device you want to buy. If it is equipped with an old sensor, then users will definitely note the fact of a long unlock with a fingerprint. In this case, it is better to consider some other model, a little more modern.
In the first gadgets with fingerprint sensors, you could only unlock the device with your fingerprint, and the devices themselves did not have such deep integration with various services as modern smartphones. But now, fingerprints can already be used to access secure areas of memory in devices, as confirmation of purchases in app stores, and as a means of authorization in various services, including banking.
Everything is going to the fact that users of mobile devices will soon forget about passwords altogether and even access to sites on the Internet will be done by fingerprint: browsers already know how to remember passwords and it costs nothing to teach them to substitute data for authentication in the required fields by fingerprint.
This function is already implemented in Samsung smartphones, but only works with the standard browser. The FIDO alliance, which includes many IT companies, including Samsung, Microsoft, Qualcomm, ARM, and many others, is going to standardize fingerprint authentication. As conceived by the alliance, it will not be necessary to store passwords from websites in the device at all: companies offer to create a cryptographic key based on a fingerprint, by which a remote server can authorize you.
While authorization on remote servers is only in FIDO plans, third-party applications on smartphones can already access the functions of fingerprint scanners. Both Apple (since iOS 8) and Google (since Android 6.0 Marshmallow) have already opened an API (an interface that provides certain functionality to third-party programs) in their operating systems, which every developer can use.
It is not always new (or well-forgotten old) technology, once it appears in a smartphone, it becomes popular. So it was with 3D displays and 3D cameras, “ultra pixels” and curved smartphones. But fingerprint scanners have a different fate, and every year they are increasingly entering our lives.
The main reason for this is that this “trick” was introduced not to brag to friends, but to solve specific problems – make using smartphones easier, speed up the process of unlocking and entering passwords, But time is always the most valuable resource.
Lyricist: Vladimir Terekhov
Popular smartphones with a fingerprint sensor
Fingerprint scanners have two main functions. With the help of the first of them, the scanner reads the image of the fingerprint, while the second function checks the match of the fingerprint with those existing in the database. Almost all modern smartphones use optical scanners. The principle of their work is similar to digital cameras.
When light hits the readable papillary pattern, an electric charge is generated by photodiodes, as a result of which a single pixel is imprinted on a future image. With the help of pixels of different intensity, a fingerprint image is formed on the scanner. In addition, before checking the print with the database, the scanner checks the quality of the image.
After taking a snapshot of the fingerprint, it is analyzed by special software using complex algorithms. By the way, there is an analysis of three types of print patterns: arc, loop and curl. After the software has determined the type of pattern, the ends of the pattern lines (breaks or bifurcations, which are called minutiae) are identified, because they are unique and can be used to identify the owner of the device.
Next comes a rather complex analysis, in which the scanner analyzes the position of the minutiae in relation to each other, with the imprint divided into microblocks. It is noteworthy that during the matching process, the scanner does not analyze a single line of the pattern. The scanner determines the match in individual blocks and determines the similarity from them.
There are two main types of optical scanners. As for the first of them, he removes the desired area of the finger by touching it directly to the scanner. This type is used in “apple” smartphones, starting with the iPhone 5s. With regard to the second type, we note that in this case the user swipes his finger over the optical scanner.
The result is a series of images that are combined into one by the software. Samsung used this type for some time in its products, however, over time, it switched to the first type, since it is more convenient, although more expensive. The main disadvantage of an optical fingerprint scanner is the vulnerability to scratches and dirt. It can also be “circled around the finger” using a cast of the phalanx of the finger.
It is also worth noting the semiconductor type of the fingerprint scanner, which is not used in smartphones for a number of reasons. It is impossible to deceive him with a cast of a finger. Another type of fingerprint scanner is the ultrasonic scanner. It has a great development prospect, and it operates on the principle of medical ultrasound. It is almost impossible to deceive him, since he is able to penetrate the epidermal layer of the skin, which is unique.
It should be noted that scanners can be placed in different parts of the smartphone. Many manufacturers install a fingerprint scanner on the back panel, the fashion has recently gone to the side face, and HMD is preparing its new flagship with an integrated scanner in the display.