New biometric method: bioacoustic signature

New biometric method: bioacoustic signature

South Korean scientists have invented a new method of biometric identification: by sound waves passing through the body (finger). It turns out that this signal is quite unique for every person. And deprived of the main vulnerability of optical biometrics methods, such as fingerprint, iris or face scan. All these methods are inherently subject to spoofing with photography of “biometric material”. This is not the case with sound waves; they cannot be photographed.

The developed system of bioacoustic frequency spectroscopy modulates microvibrations, which spread through the body and generate a unique spectral response. In the tests, the characteristic was maintained for two months and ensured the accuracy of verification of 41 subjects at 97.16%.

It is predicted that as the Internet of things and smart things spread, biometric identity will become more important. Ordinary biometric authentication relies on images of the human body. But as mentioned above, these images can be copied by attackers. Fingerprints are the easiest to forge.

Fingerprint forgery

Human fingerprints can be photographed on a glass surface, on a smartphone, door handle or other smooth surface, printed, etched on a circuit board, then make a copy of gelatin – and the “artificial finger” is ready.

More reliable variant with the use of pebble and carpenter glue, which works against Apple TouchID:

  1. The print is photographed or scanned at 2400 dpi resolution. You can scan directly from the TouchID sensor surface by putting your smartphone into the scanner.
  2. In the photo editor, the image is converted to a black-and-white picture, inverted and mirrored.
  3. The image is printed on transparent pebbles with a resolution of 1200 dpi.
  4. The resulting mask is exposed on a light-sensitive PCB in UV flight.Structures protected against ultraviolet by black areas do not harden and can be removed. This creates a shape that serves as a template for artificial fingerprints.

  5. A thin layer of graphite is applied to the shape for better interaction with TouchID capacitive sensors.
  6. Then a carpentry glue is applied to the form.It serves as a skin-like carrier material. Such an overlay on your finger allows you to fool your fingerprint scanners.


Rainbow Sheath Fake

Eye iris recognition systems are considered more accurate, although a fake iris is also made from a person’s photo using a high-resolution printer and conventional contact lenses (see Eye iris scanner Samsung Galaxy S8).

To copy the iris is enough a photo of a person taken from a medium distance in night mode (for infrared spectrum). The photo is printed on a laser printer with such a calculation that the iris size is the same as the contact lens. Then the contact lens is superimposed on the sheet and the phone is unlocked by this photo.

Alternate biometrics

To address these problems, researchers are proposing alternative methods of biometrics, including authentication with pen-penalm, the contour of the earthe knuckles, nasal, and combined approachesmultimodal biometrics. However, all these technologies are still dependent on the structural characteristics of the resulting optical image and are therefore subject to forgery using copied biometrics.

Bioacoustic signature

The new biometric authentication platform works in a fundamentally different way. It is based on a biodynamic finger reaction in the acoustic spectrum. This is the first scientific work that suggests using biacoustics in this way. Previous acoustic methods were limited to voice recognition and breathing sound signatures, while other options remained relatively unexplored.

Below is a schematic illustration of the platform and concept of an acoustic identification system, which uses the transmission of vibratory signals through the bones and tissue of the finger.

(a) concept; (b) anatomical finger structure, location of the microphone and transducer (transmitter) on the distal phalange and metacarpal bone; (c) system diagram: sinusoidal signal is received at the input of the transducer and transmitted through the finger, perceived by microphone, demodulated by means of the reference signal, filtered by the low-pass filter and digitized by analog-to-digital transducer of microcontroller; (d) photo of the hand on the device; (e) X-ray image of the hand with the location of sensors; (f) map of the magnitude of the empirically measured acoustic signal from the transducer, located at the end of the metacarpal phalangea.

The illustration shows how the proposed bioacoustic sensing scheme works. When people touch an object with their hand, microvibrations spread through their fingers and hand, carrying information about the objects they interact with. The acoustic signal is transmitted differently due to the anatomical features of each body. Thus, the signal contains anatomical information about the body structure, namely bone, cartilage, tendon and muscle tissue – and relies on their geometry as well as their biomechanical properties.

For authentication, the user places his finger on the platform where the signal transmitter (transducer) and the acoustic sensor are placed. The excitation and sensing locations are selected so that the acoustic signal passed through the proximal and middle phalanges of the finger. In particular, the acoustic sensor is located 3 mm above the front distal interphalangeal fold, which is the lower end of the distal phalanx. The transmitter is located 50 mm from the acoustic sensor, completely covering the length of the middle phalanx of the finger.

Experiments have shown that the individual shape of the signal is preserved with different forces of finger pressure.

Repeatability (c) and signal shape at different pressing forces (d).

The measurement was made in the range from 100 Hz to 3 kHz in 10 Hz steps, which took 15 seconds. It may be possible to optimize these characteristics as the hardware improves.

At the beginning of the experiment, the scientists were worried that the signal would be variable due to changes in tissue and cells. So the experiments were repeated three times at 30-day intervals. They were surprised to find that the bioacoustic signature had not changed at all during this time. Although it can be assumed that as humans grow older and older, their anatomical structure does change significantly enough to affect the shape of the signal.

This research has also had an unexpected effect. Bioacoustic frequency spectroscopy proved to be so accurate in tissue analysis that inventors began to explore the possibility of its application even for the diagnosis of skeletal-muscular disease.

Scientific article describing the bioacoustic signature published in the journal IEEE Transactions on Cybernetics (doi: 10.1109/TCYB.2019.2941281).


Source – HABR

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