What is your perception of fingerprints, phone unlock, and the dead? Do you think using a deceased person’s fingerprint to unlock his phone is possible?
In March 2020, Yuri Vinogradov a Belarusian, posted a video showing how he used a broken thumb to successfully unlock a fingerprint-protected smartphone.
Of course, he didn’t cut off his fingers deliberately. His father accidentally sawn off his fingers when he was operating the circular saw two months ago.
His father usually used broken fingers to unlock the phone, which was frozen. Vinogradov said that he often sees in the movie the bridge segment where the other party’s fingerprints are successfully decrypted, so he wants to verify whether it is feasible.
Can A Severed Finger Be Used to Unlock A Phone?
He put his severed finger in hot water and used it to unlock his phone smoothly. For the records, the severed finger was heated to room temperature.
So he concluded that unlocking the smartphone with a severed finger is entirely feasible. However, I think this experiment is accidental and cannot represent all smartphones.
However, this event reminds me of a topic that was once hotly discussed on the Internet: after death, can fingerprints unlock mobile phones?
Apparently, both the severed finger and the corpse have stopped normal cell activity and blood transmission and have lost their biological activity.
If the severed finger can successfully unlock the fingerprint lock, does it mean the corpse is also OK?
To know whether your fingerprint can unlock your phone after death, you must understand the principle of fingerprint unlocking.
Let’s get to know the Principle of Fingerprints Unlocking
Fingerprints are a kind of magical existence. As you can see from the images above, there are only three types: skip pattern, bucket pattern, and bow pattern.
Interestingly, almost no two fingerprints are exactly the same in the world. Even if they are identical twins, their patterns are highly similar, but the details and features differ.
Everyone’s fingerprints will remain the same from birth to death. Because of their uniqueness and singularity, fingerprints have always been used to assist criminal investigations, replace signatures and seals, or divination. After the development of smartphones, fingerprints were used to unlock the phone.
Types of Fingerprints
The first fingerprint unlocking phone is a push fingerprint unlocking smartphone released by Motorola Atrix, which uses an optical sensor technology. The phone is unlocked by scanning your finger once or multiple times.
However, this phone does not scan fingerprints but scans by fingers—number of times to unlock.
The first fingerprint to unlock a smartphone
So How Does the Real Fingerprint Unlocking Work?
Fingerprint unlocking has a set of fingerprint recognition algorithms to complete the unlocking through acquisition, image preprocessing, data feature extraction, and feature matching.
Step 1: Collect Fingerprints
When we get a new mobile phone with a fingerprint unlocking function, we will enroll/enlist fingerprints first.
At this time, the mobile phone will collect your fingerprint information. In terms of collection methods, there are mainly “sliding types” and “pressing types”.
Although the sliding type is low in cost, the collection success rate is also low. It requires continuous and standardized sliding motions to collect the data successfully.
So the most common collection method is the push type. The push-type is to press the finger to unlock the part on the sensor several times and piece together a large area of the fingerprint pattern.
Step 2: Image Preprocessing
After the fingerprints are collected, the quality of the image will be evaluated. In addition, the images will be enhanced and refined to deal with interferences such as removing burrs, breaks, and the like.
Step 3: Extract Features
After obtaining a clear image, the features should then be extracted. Technically, the pre-processed image will have many false feature points, affecting the fingerprint recognition performance and causing the false rejection rate and the false recognition rate to increase.
The extracted feature data will be stored after the false feature points are removed.
Step 4: Feature Matching
The quality of the feature-matching algorithm directly affects the performance, speed, and efficiency of recognition. The point-matching algorithm based on fingerprint structure features matches the calibrated point set.
Comparatively, the fingerprint identification method differs mainly from the image acquisition method.
How can we differentiate the various fingerprint technologies of capacitive, ultrasonic, and image optical fingerprint identification?
Principles of Commonly Used Fingerprint Recognition Technology
Capacitive Fingerprint Unlock
Capacitive fingerprint recognition technology is mobile phones’ most commonly used fingerprint recognition method.
Human cell activities will generate a weak current, and the fingerprint lines are microscopically uneven, so the contact between the silicon wafer and the skin’s electrolyte can form an electric field.
At this time, the sensor can collect the shape of the fingerprint and obtain the image. This will later be used to unlock. Through this principle, we can understand that the phone lock with capacitive recognition technology cannot be unlocked when there is sweat or water on the hand.
Similarly, the under-screen fingerprint scanner will also not work due to complex electric field conditions. Hence, this method is more common in the home button unlocking, and The rear is unlocked.
Ultrasonic Fingerprint Recognition
Ultrasonic fingerprint recognition can penetrate different materials. After scanning the finger with a specific frequency, the fingerprint ridges and valleys can be distinguished according to the generated echoes, and the corresponding images can be established.
Ultrasonic fingerprint recognition can penetrate metal, glass, and other materials and realize fingerprint recognition under the screen. At the same time, ultrasonic fingerprint recognition is basically not affected by dirt, water, etc., on the surface of the finger.
Optical fingerprint Recognition
Optical recognition is an earlier fingerprint recognition technology. It usually comprises a light source and a triangular prism photosensitive component.
The light emitted by the light source passes through a prism and then irradiates the finger surface. The light reflected from the finger surface carries fingerprint information and is projected onto the photosensitive component through the prism again.
After the sensory component recognizes the fingerprint information, the unlock is realized. Traditional optical technology is used in attendance machines, access control, and security inspection systems. Optical recognition can also be used for under-screen fingerprint unlocking on a full screen.
However, regardless of whether the body itself has electricity or not, capacitive fingerprint recognition technology seems to be prone to bypass.
Fingerprints, Phone Unlock and the Dead
On April 8, 2020, an intelligence agency named Talos used 3D printing technology to forge fingerprints and unlocked 8 different types of fingerprint unlocking devices with a success rate of 80%.
The materials they used for printing were resin, clay for carving, etc., and they made more than 50 molds.
They solved the problem of the fingerprint image’s clarity and the material’s conductivity, and the sensor was successfully activated and unlocked.
In conclusion, even if the human body loses biological activity and the fingers become “lifeless”, and electricity is applied to the deceased’s fingerprint before the deceased’s fingerprint is deformed, an electric current will flow through the deceased’s fingers.
It is, therefore, possible to unlock the phone through the fingerprint. Of course, this is just a theoretical guess.