On Adversarial Gait Recognition

Biometric product marketing expert.

You’ve presumably noticed the multiple biometrics on display in my “landscape” reel. Fingers, a face, irises, a voice, veins, and even DNA.

But you may have missed one.

Gait.

I still remember the time that I ran into a former coworker from my pre-biometric years, and she said she recognized me by the way I walk.

But it’s no surprise that gait recognition is susceptible to spoofing.

“[A]dversarial Gait Recognition has arisen as a major challenge in video surveillance systems, as deep learning-based gait recognition algorithms become more sensitive to adversarial attacks.”

So Zeeshan Ali and others are working on IMPROVING gait-based adversarial attacks…the better to counter them.

“Our technique includes two major components: AdvHelper, a surrogate model that simulates the target, and PerturbGen, a latent-space perturbation generator implemented in an encoder-decoder framework. This design guarantees that adversarial samples are both effective and perceptually realistic by utilizing reconstruction and perceptual losses. Experimental results on the benchmark CASIA-gait dataset show that the proposed method achieves a high attack success rate of 94.33%.”

Now we need to better detect these adversarial attacks.

A silly walk, but on Fawlty Towers.

Let’s Talk About Occluded Face Expression Reconstruction

ORFE, OAFR, ORecFR, OFER. Let’s go!

As you may know, I’ve often used Grok to convert static images to 6-second videos. But I’ve never tried to do this with an occluded face, because I feared I’d probably fail. Grok isn’t perfect, after all.

Facia’s 2024 definition of occlusion is “an extraneous object that hinders the view of a face, for example, a beard, a scarf, sunglasses, or a mustache covering lips.” Facia also mentions the COVID practice of wearing masks.

Occlusion limits the data available to facial recognition algorithms, which has an adverse effect on accuracy. At the time, “lower chin and mouth occlusions caused an inaccuracy rate increase of 8.2%.” Occlusion of the eyes naturally caused greater inaccuracies.

So how do we account for occlusions? Facia offers three tactics:

  • Occlusion Robust Feature Extraction (ORFE)
  • Occlusion Aware Facial Recognition (OAFR)
  • Occlusion Recovery-Based Facial Recognition (ORecFR)

But those acronyms aren’t enough, so we’ll add one more.

At the 2025 Computer Vision and Pattern Recognition conference, a group of researchers led by Pratheba Selvaraju presented a paper entitled “OFER: Occluded Face Expression Reconstruction.” This gives us one more acronym to play around with.

Here’s the abstract of the paper:

Reconstructing 3D face models from a single image is an inherently ill-posed problem, which becomes even more challenging in the presence of occlusions. In addition to fewer available observations, occlusions introduce an extra source of ambiguity where multiple reconstructions can be equally valid. Despite the ubiquity of the problem, very few methods address its multi-hypothesis nature. In this paper we introduce OFER, a novel approach for singleimage 3D face reconstruction that can generate plausible, diverse, and expressive 3D faces, even under strong occlusions. Specifically, we train two diffusion models to generate a shape and expression coefficients of face parametric model, conditioned on the input image. This approach captures the multi-modal nature of the problem, generating a distribution of solutions as output. However, to maintain consistency across diverse expressions, the challenge is to select the best matching shape. To achieve this, we propose a novel ranking mechanism that sorts the outputs of the shape diffusion network based on predicted shape accuracy scores. We evaluate our method using standard benchmarks and introduce CO-545, a new protocol and dataset designed to assess the accuracy of expressive faces under occlusion. Our results show improved performance over occlusion-based methods, while also enabling the generation of diverse expressions for a given image.

Cool. I was just writing about multimodal for a biometric client project, but this is a different meaning altogether.

In my non-advanced brain, the process of creating multiple options and choosing the one with the “best” fit (however that is defined) seems promising.

Although Grok didn’t do too badly with this one. Not perfect, but pretty good.

Grok.

Another Voice Deepfake Fraud Scam

Time for another voice deepfake scam.

This one’s in Schwyz, in Switzerland, which makes reading of the original story somewhat difficult. But we can safely say that “Eine unbekannte Täterschaft hat zur Täuschung künstliche Intelligenz eingesetzt und so mehrere Millionen Franken erbeutet” is NOT a good thing.

And that’s millions of Swiss francs, not millions of Al Frankens.

Millions of Al Frankens.

Luckily, someone at Biometric Update speaks German well enough to get the gist of the story.

“Deploying audio manipulated to sound like a trusted business partner, fraudsters bamboozled an entrepreneur from the canton of Schwyz into transferring “several million Swiss francs” to a bank account in Asia.”

And what do the canton police recommend? (Google Translated)

“Be wary of payment requests via telephone or voice message, even if the voice sounds familiar.”

On Acquired Identities

Most of my discussions regarding identity assume the REAL identity of a person.

But what if someone acquires the identity of another? For example, when the late Steve Bridges impersonated George W. Bush?

White House photo by Kimberlee Hewitt – whitehouse.gov, President George W. Bush and comedian Steve Bridges, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3052515

Or better still, what when multiple people adopt an identity?

Google Gemini.

And by the way, Charlie Chaplin said that he NEVER entered a Charlie Chaplin lookalike contest…and came in third.

Grok.

Of course, these assumed identities require alterations that liveness detection should detect.

As a biometric product marketing expert should know.

Landscape.

Singer/songwriters…and Deepfakes

I was just talking about singers, songwriters, and one singer who pretended to be a songwriter.

Of course, some musicians can be both.

Willie Nelson has written songs for others, sung songs written by others, and sung his own songs.

But despite the Grok deepfake I shared last October, Willie is not known as a rapper.

This is fake. Grok.

Step Into Christmas: Deepfake?

Deepfakes are not a 21st century invention. Take this video of “Step Into Christmas.”

But here are the musician credits.

Elton: Piano and vocals

Davey Johnstone: Guitars and backing vocals

Dee Murray: Bass guitar and backing vocals

Nigel Olsson: Drums and backing vocals

Ray Cooper: Percussion

Kiki Dee: Backing vocals (uncredited)

Jo Partridge: Backing vocals (uncredited)

Roger Pope: Tambourine (uncredited)

David Hentschel: ARP 2500 synthesizer (uncredited)

The video doesn’t match this list. According to the video, Elton played more than the guitar, and Bernie Taupin performed on the track.

So while we didn’t use the term “deepfake” in 1973, this promotional video meets at least some of the criteria of a deepfake.

And before you protest that everybody knew that Elton John didn’t play guitar…undoubtedly some people saw this video and believed that Elton was a guitarist. After all, they saw it with their own eyes.

Sounds like fraud to me!

Remember this when you watch things.