Biometric Authentication by Grinding Your Tooth



Two current analysis papers from the US and China have proposed a novel answer for teeth-based authentication: simply grind or chunk your enamel a bit, and an ear-worn system (an ‘earable’, that will additionally double up as an everyday audio listening system) will acknowledge the distinctive aural sample produced by abrading your dental structure, and generate a sound biometric ‘go’ to a suitably outfitted problem system.

Various ear-worn prototype devices for the two systems. Sources: (ToothSonic) and (TeethPass)

Varied ear-worn prototype units for the 2 techniques. Sources: (ToothSonic) and (TeethPass)

Prior strategies of dental authentication (i.e. for dwelling folks, slightly than forensic identification), have wanted the person to ‘grin and naked’, so {that a} dental recognition system might affirm that their enamel matched biometric information. In summer time of 2021, a analysis group from India made headlines with such a system, titled DeepTeeth.

The brand new proposed techniques, dubbed ToothSonic and TeethPass, come respectively from a tutorial collaboration between Florida State College and Rutgers College in america; and a joint effort between researchers at Beijing Institute of Expertise, Tsinghua College, and Beijing College of Expertise, working with the Division of Laptop and Info Sciences at Temple College in Philadelphia.


The fully US-based ToothSonic system has been proposed within the paper Ear Wearable (Earable) Person Authentication through Acoustic Toothprint.

The ToothSonic authors state:

‘ToothSonic [leverages] the toothprint-induced sonic impact produced by customers performing enamel gestures for earable authentication. Specifically, we design consultant enamel gestures that may produce efficient sonic waves carrying the knowledge of the toothprint.

‘To reliably seize the acoustic toothprint, it leverages the occlusion impact of the ear canal and the inward-facing microphone of the earables. It then extracts multi-level acoustic options to mirror the intrinsic toothprint info for authentication.’

Contributing impact factors that formulate a unique aural toothprint registered in an ear-worn device. Source:

Contributing influence components that formulate a singular aural toothprint registered in an ear-worn system. Supply:

The researchers word an a variety of benefits of aural tooth/cranium signature patterns, which additionally apply to the primarily Chinese language undertaking. For example, it could be terribly difficult to imitate or spoof the toothprint, which should journey by way of the distinctive structure of the pinnacle tissues and cranium channel earlier than arriving at a recordable ‘template’ in opposition to which future authentications could be examined.

Moreover, toothprint-based identification not solely eliminates the potential embarrassment of grinning or grimacing for a cell or mounted digicam, however removes the necessity for the person to in any approach distract themselves from probably vital actions comparable to working autos.

Moreover this, the tactic is appropriate for many individuals with motor impairments, whereas the units can probably be integrated into earbuds whose main utilization is much extra frequent (i.e. listening to music and making phone calls), eradicating the necessity for devoted, standalone authentication units, or recourse to cell purposes.

Additional, the potential of reproducing an individual’s dentition in a spoof assault (i.e. by printing a photograph from an uninhibited social media picture publish), and even replicating their enamel within the unlikely state of affairs of acquiring complicated and full dental molds, is obviated by the very fact the sounds abrading enamel make are filtered by way of utterly hidden inner geometry of the jaw and the auditory canal.

From the TeethPass paper, the occluding effect of the ear canal makes casual reproduction or imitation effectively impossible.

From the TeethPass paper, the occluding impact of the ear canal makes informal replica or imitation successfully inconceivable.

As an assault vector, the one remaining alternative (moreover forcible and bodily coercion of the person) is to realize database entry to the host safety system and fully substitute the person’s recorded aural tooth sample with the attacker’s personal sample (since illicitly acquiring any individual else’s toothprint wouldn’t result in any sensible methodology of authentication).

Workflow for ToothSonic.

Workflow for ToothSonic.

Although there’s a tiny alternative for an attacker to playback a recording of the mastication in their very own mouths, the Chinese language-led undertaking discovered that this isn’t solely a conspicuous however very ill-starred strategy, with minimal likelihood of success (see beneath).

A Distinctive Smile

The ToothSonic paper outlines the various distinctive traits in a person’s dentition, together with courses of occlusion (comparable to overbite), enamel density and resonance, lacking aural info from extracted enamel, distinctive traits of porcelain and metallic substitutions (amongst different attainable supplies), and cusp morphology, amongst many different attainable distinguishing options.

The authors state:

‘[The] toothprint-induced sonic waves are captured through the person’s non-public teeth-ear channel. Our system thus is proof against superior mimic and replay assaults because the person’s non-public teeth-ear channel secures the sonic waves, that are unlikely uncovered by adversaries.’

Since jaw motion has a restricted vary of mobility, the authors envisage ten attainable manipulations that may very well be recorded as viable biometric prints, illustrated beneath as ‘superior enamel gestures’:

A few of these actions are harder to realize than others, although the harder actions don’t end in patterns which can be any roughly straightforward to copy or spoof than much less difficult actions.

Macro-level traits of apposite enamel actions are extracted utilizing a Gaussian combination mannequin (GMM) speaker identification system. Mel-frequency cepstral coefficients (MFCCs), a illustration of sound, are obtained for every of the attainable actions.

Six different sliding gestures for the same subject during MFCC extraction under the TeethPass system.

Six totally different sliding gestures for a similar topic throughout MFCC extraction below the TeethPass system.

The ensuing signature sonic wave that contains the distinctive biometric signature is extremely susceptible to sure human physique vibrations; due to this fact ToothSonic imposes a filter band between 20-8000Hz.

Sonic wave segmentation is achieved through a Hidden Markov Mannequin (HMM), in accordance with two prior works from Germany.

For the authentication mannequin, derived options are fed into a totally related neural community, traversing varied layers till activation through ReLU. The final absolutely related layer makes use of a Softmax perform to generate the outcomes and predicted label for an authentication state of affairs.

The coaching database was obtained by asking 25 contributors (10 feminine, 15 male) to put on an adulterated earbud in real-world environments, and conducting their regular actions. The prototype earbud (see first picture above) was created at a price of some {dollars} with off-the-shelf client {hardware}, and options one microphone chip. The researchers contend {that a} business implementation of comparable to system could be eminently inexpensive to provide.

The educational mannequin comprised the neural community classifiers in MATLAB, skilled at a studying fee of 0.01, with LBFGS because the loss perform. Analysis strategies for authentication had been FRR, FAR and BAC.

General efficiency for ToothSonic was superb, relying on the issue of the interior mouth gesture being carried out:

Outcomes had been obtained throughout three grades of issue of mouth gesture: snug, much less snug, and have difficulties.  One of many person’s most well-liked gestures achieved an accuracy fee of 95%.

By way of limitations, the customers concede that adjustments in enamel over time will doubtless require a person to re-imprint the aural tooth signature, as an illustration after notable dental work. Moreover, enamel high quality can degrade or in any other case change over time, and the researchers recommend that older folks may be requested to replace their profiles periodically.

The authors additionally concede that multi-use earbuds of this nature would require the person to pause music or dialog throughout authentication (in frequent with the Chinese language-led TeethPass), and that many at the moment out there earbuds should not have the required computational energy to facilitate comparable to system.

Regardless of this, they observe*:

‘Encouragingly, current releases of the Apple H1 chip within the Airpods Professional and QCS400 by Qualcomm are succesful to help voice-based on-device AI. It implies that implementing ToothSonic on earable may very well be realized in close to future.’

Nevertheless, the paper concedes that this extra processing might influence battery life.


Launched within the paper TeethPass: Dental Occlusion-based Person Authentication through In-ear Acoustic Sensing, The Chinese language-American undertaking operates on a lot the identical basic ideas as ToothSonic, accounting for the traversal of signature audio from dental abrasion by way of the auditory canal and intervening bone buildings.

Air noise removing is carried out on the information gathering stage, mixed with noise discount and – as with the ToothSonic strategy – an acceptable frequency filter is imposed for the aural signature.

System architecture for TeethPass.

System structure for TeethPass.

The ultimate extracted MFCC options are used to coach a Siamese neural community.

Structure of the Siamese neural network for TeethPass.

Construction of the Siamese neural community for TeethPass.

Analysis metrics for the system had been FRR, FAR, and a confusion matrix. As with ToothSonic, the system was discovered to be strong to 3 varieties of attainable assault: mimicry, replay, and hybrid assault. In a single occasion, the researchers tried an assault by taking part in the sound of a person’s dental motion contained in the mouth of an attacker, with a small speaker, and located that at distances lower than 20cm, this hybrid assault methodology has a better than 1% likelihood of success.

In all different eventualities, the impediment of mimicking the goal’s interior cranium building, as an illustration throughout a replay assault, makes a ‘hijacking’ state of affairs among the many least doubtless threat in the usual run of biometric authentication frameworks.

In depth experiments demonstrated that TeethPass achieved a mean authentication accuracy of 98.6%, and will resist 98.9% of spoofing assaults.


* My conversion of the authors’ inline quotation/s to hyperlink/s

First revealed 18th April 2022.



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