Fooling a Voice Authentication System with an AI-Generated Voice
A reporter used an AI synthesis of his own voice to fool the voice authentication system for Lloyd’s Bank.
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A reporter used an AI synthesis of his own voice to fool the voice authentication system for Lloyd’s Bank.
This is interesting research:
In this paper, we develop a new mechanism for detecting audio deepfakes using techniques from the field of articulatory phonetics. Specifically, we apply fluid dynamics to estimate the arrangement of the human vocal tract during speech generation and show that deepfakes often model impossible or highly-unlikely anatomical arrangements. When parameterized to achieve 99.9% precision, our detection mechanism achieves a recall of 99.5%, correctly identifying all but one deepfake sample in our dataset.
From an article by two of the researchers:
The first step in differentiating speech produced by humans from speech generated by deepfakes is understanding how to acoustically model the vocal tract. Luckily scientists have techniques to estimate what someone—or some being such as a dinosaur—would sound like based on anatomical measurements of its vocal tract.
We did the reverse. By inverting many of these same techniques, we were able to extract an approximation of a speaker’s vocal tract during a segment of speech. This allowed us to effectively peer into the anatomy of the speaker who created the audio sample.
From here, we hypothesized that deepfake audio samples would fail to be constrained by the same anatomical limitations humans have. In other words, the analysis of deepfaked audio samples simulated vocal tract shapes that do not exist in people.
Our testing results not only confirmed our hypothesis but revealed something interesting. When extracting vocal tract estimations from deepfake audio, we found that the estimations were often comically incorrect. For instance, it was common for deepfake audio to result in vocal tracts with the same relative diameter and consistency as a drinking straw, in contrast to human vocal tracts, which are much wider and more variable in shape.
This is, of course, not the last word. Deepfake generators will figure out how to use these techniques to create harder-to-detect fake voices. And the deepfake detectors will figure out another, better, detection technique. And the arms race will continue.
It’s the eyes:
The researchers note that in many cases, users can simply zoom in on the eyes of a person they suspect may not be real to spot the pupil irregularities. They also note that it would not be difficult to write software to spot such errors and for social media sites to use it to remove such content. Unfortunately, they also note that now that such irregularities have been identified, the people creating the fake pictures can simply add a feature to ensure the roundness of pupils.
And the arms race continues….
“Markpainting” is a clever technique to watermark photos in such a way that makes it easier to detect ML-based manipulation:
An image owner can modify their image in subtle ways which are not themselves very visible, but will sabotage any attempt to inpaint it by adding visible information determined in advance by the markpainter.
One application is tamper-resistant marks. For example, a photo agency that makes stock photos available on its website with copyright watermarks can markpaint them in such a way that anyone using common editing software to remove a watermark will fail; the copyright mark will be markpainted right back. So watermarks can be made a lot more robust.
Here’s the paper: “Markpainting: Adversarial Machine Learning Meets Inpainting,” by David Khachaturov, Ilia Shumailov, Yiren Zhao, Nicolas Papernot, and Ross Anderson.
Abstract: Inpainting is a learned interpolation technique that is based on generative modeling and used to populate masked or missing pieces in an image; it has wide applications in picture editing and retouching. Recently, inpainting started being used for watermark removal, raising concerns. In this paper we study how to manipulate it using our markpainting technique. First, we show how an image owner with access to an inpainting model can augment their image in such a way that any attempt to edit it using that model will add arbitrary visible information. We find that we can target multiple different models simultaneously with our technique. This can be designed to reconstitute a watermark if the editor had been trying to remove it. Second, we show that our markpainting technique is transferable to models that have different architectures or were trained on different datasets, so watermarks created using it are difficult for adversaries to remove. Markpainting is novel and can be used as a manipulation alarm that becomes visible in the event of inpainting.
Researchers can detect deep fakes because they don’t convincingly mimic human blood circulation in the face:
In particular, video of a person’s face contains subtle shifts in color that result from pulses in blood circulation. You might imagine that these changes would be too minute to detect merely from a video, but viewing videos that have been enhanced to exaggerate these color shifts will quickly disabuse you of that notion. This phenomenon forms the basis of a technique called photoplethysmography, or PPG for short, which can be used, for example, to monitor newborns without having to attach anything to a their very sensitive skin.
Deep fakes don’t lack such circulation-induced shifts in color, but they don’t recreate them with high fidelity. The researchers at SUNY and Intel found that “biological signals are not coherently preserved in different synthetic facial parts” and that “synthetic content does not contain frames with stable PPG.” Translation: Deep fakes can’t convincingly mimic how your pulse shows up in your face.
The inconsistencies in PPG signals found in deep fakes provided these researchers with the basis for a deep-learning system of their own, dubbed FakeCatcher, which can categorize videos of a person’s face as either real or fake with greater than 90 percent accuracy. And these same three researchers followed this study with another demonstrating that this approach can be applied not only to revealing that a video is fake, but also to show what software was used to create it.
Of course, this is an arms race. I expect deep fake programs to become good enough to fool FakeCatcher in a few months.
Presidential campaign season is officially, officially, upon us now, which means it’s time to confront the weird and insidious ways in which technology is warping politics. One of the biggest threats on the horizon: artificial personas are coming, and they’re poised to take over political debate. The risk arises from two separate threads coming together: artificial intelligence-driven text generation and social media chatbots. These computer-generated “people” will drown out actual human discussions on the Internet.
Text-generation software is already good enough to fool most people most of the time. It’s writing news stories, particularly in sports and finance. It’s talking with customers on merchant websites. It’s writing convincing op-eds on topics in the news (though there are limitations). And it’s being used to bulk up “pink-slime journalism”—websites meant to appear like legitimate local news outlets but that publish propaganda instead.
There’s a record of algorithmic content pretending to be from individuals, as well. In 2017, the Federal Communications Commission had an online public-commenting period for its plans to repeal net neutrality. A staggering 22 million comments were received. Many of them—maybe half—were fake, using stolen identities. These comments were also crude; 1.3 million were generated from the same template, with some words altered to make them appear unique. They didn’t stand up to even cursory scrutiny.
These efforts will only get more sophisticated. In a recent experiment, Harvard senior Max Weiss used a text-generation program to create 1,000 comments in response to a government call on a Medicaid issue. These comments were all unique, and sounded like real people advocating for a specific policy position. They fooled the Medicaid.gov administrators, who accepted them as genuine concerns from actual human beings. This being research, Weiss subsequently identified the comments and asked for them to be removed, so that no actual policy debate would be unfairly biased. The next group to try this won’t be so honorable.
Chatbots have been skewing social-media discussions for years. About a fifth of all tweets about the 2016 presidential election were published by bots, according to one estimate, as were about a third of all tweets about that year’s Brexit vote. An Oxford Internet Institute report from last year found evidence of bots being used to spread propaganda in 50 countries. These tended to be simple programs mindlessly repeating slogans: a quarter million pro-Saudi “We all have trust in Mohammed bin Salman” tweets following the 2018 murder of Jamal Khashoggi, for example. Detecting many bots with a few followers each is harder than detecting a few bots with lots of followers. And measuring the effectiveness of these bots is difficult. The best analyses indicate that they did not affect the 2016 US presidential election. More likely, they distort people’s sense of public sentiment and their faith in reasoned political debate. We are all in the middle of a novel social experiment.
Over the years, algorithmic bots have evolved to have personas. They have fake names, fake bios, and fake photos—sometimes generated by AI. Instead of endlessly spewing propaganda, they post only occasionally. Researchers can detect that these are bots and not people, based on their patterns of posting, but the bot technology is getting better all the time, outpacing tracking attempts. Future groups won’t be so easily identified. They’ll embed themselves in human social groups better. Their propaganda will be subtle, and interwoven in tweets about topics relevant to those social groups.
Combine these two trends and you have the recipe for nonhuman chatter to overwhelm actual political speech.
Soon, AI-driven personas will be able to write personalized letters to newspapers and elected officials, submit individual comments to public rule-making processes, and intelligently debate political issues on social media. They will be able to comment on social-media posts, news sites, and elsewhere, creating persistent personas that seem real even to someone scrutinizing them. They will be able to pose as individuals on social media and send personalized texts. They will be replicated in the millions and engage on the issues around the clock, sending billions of messages, long and short. Putting all this together, they’ll be able to drown out any actual debate on the Internet. Not just on social media, but everywhere there’s commentary.
Maybe these persona bots will be controlled by foreign actors. Maybe it’ll be domestic political groups. Maybe it’ll be the candidates themselves. Most likely, it’ll be everybody. The most important lesson from the 2016 election about misinformation isn’t that misinformation occurred; it is how cheap and easy misinforming people was. Future technological improvements will make it all even more affordable.
Our future will consist of boisterous political debate, mostly bots arguing with other bots. This is not what we think of when we laud the marketplace of ideas, or any democratic political process. Democracy requires two things to function properly: information and agency. Artificial personas can starve people of both.
Solutions are hard to imagine. We can regulate the use of bots—a proposed California law would require bots to identify themselves—but that is effective only against legitimate influence campaigns, such as advertising. Surreptitious influence operations will be much harder to detect. The most obvious defense is to develop and standardize better authentication methods. If social networks verify that an actual person is behind each account, then they can better weed out fake personas. But fake accounts are already regularly created for real people without their knowledge or consent, and anonymous speech is essential for robust political debate, especially when speakers are from disadvantaged or marginalized communities. We don’t have an authentication system that both protects privacy and scales to the billions of users.
We can hope that our ability to identify artificial personas keeps up with our ability to disguise them. If the arms race between deep fakes and deep-fake detectors is any guide, that’ll be hard as well. The technologies of obfuscation always seem one step ahead of the technologies of detection. And artificial personas will be designed to act exactly like real people.
In the end, any solutions have to be nontechnical. We have to recognize the limitations of online political conversation, and again prioritize face-to-face interactions. These are harder to automate, and we know the people we’re talking with are actual people. This would be a cultural shift away from the internet and text, stepping back from social media and comment threads. Today that seems like a completely unrealistic solution.
Misinformation efforts are now common around the globe, conducted in more than 70 countries. This is the normal way to push propaganda in countries with authoritarian leanings, and it’s becoming the way to run a political campaign, for either a candidate or an issue.
Artificial personas are the future of propaganda. And while they may not be effective in tilting debate to one side or another, they easily drown out debate entirely. We don’t know the effect of that noise on democracy, only that it’ll be pernicious, and that it’s inevitable.
This essay previously appeared in TheAtlantic.com.
EDITED TO ADD: Jamie Susskind wrote a similar essay.
EDITED TO ADD (3/16): This essay has been translated into Spanish.
EDITED TO ADD (6/4): This essay has been translated into Portuguese.
Sidebar photo of Bruce Schneier by Joe MacInnis.