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What You Should Know Before Leaking a Zoom Meeting
- xxpor 6y agoNext week on HN: Show HN: zoom-dewatermarker (github.com) Seriously though, I doubt what Zoom is adding (specifically for audio) is anything that new. Does anyone have experience removing this type of stuff? Would something like a bandpass filter for say, 100 Hz-15 kHz work?
- S_A_P 6y agoThat is my first thought. I have a few specialty plugins in Wavelab that I would be curious to run a Zoom capture through. If its ultrasonic, then as you say a low pass filter should suffice, but theres a million ways to encode data...
- vorpalhex 6y agoI mean, should be as easy as recording your own zoom call with the Watermark enabled and a well known audio track (a metronome, dead silence, etc). Rip audio from the recording and examine it for anything outside of the metronome. Probably need to do this several times for different participants and meetings to get an idea of what the watermark looks like and where in the spectrum it sits.
- Mistri 6y agoPerhaps they have countermeasures for this? Maybe a unique identifier for each meeting that alters the audio signature.
- vorpalhex 6y agoThat's why it'd be necessary to record several meetings and see how things change between them.
- sumtechguy 6y agoEasier way would be to get 2 copies of the same stream from 2 or more clients then compare. Repeat until extra/missing data is found.
- mpoteat 6y agoFrom my perspective, the only fool proof way of removing all audio watermarks from a conversation is to run individual speaker detection, STT detection, and voice cloning algorithms to "recreate" the conversation from scratch. Even things like background electrical hum have been used in audio forensics.
- farnsworth 6y agoI've seen the demos of AI systems that can be trained on an individual's voice, and generate new speech in the same voice. If I was waterprinting a meeting, I would train a system like this on the fly on the people in the meeting and use it to dynamically insert filler words (um...) in a unique pattern into the audio stream for each member of the meeting. That would defeat any audio filter tricks or recreating the meeting from scratch, so you would want to summarize/rephrase the meeting too.
- bobthepanda 6y agoHow would you explain these filler words if the lips don’t match?
- loa_in_ 6y agoBut if certain frequencies are in the training data, they still will be in the output. Won't you end up with watermarked audio still?
- ardy42 6y ago> I've seen the demos of AI systems that can be trained on an individual's voice, and generate new speech in the same voice. If I was waterprinting a meeting, I would train a system like this on the fly on the people in the meeting and use it to dynamically insert filler words (um...) in a unique pattern into the audio stream for each member of the meeting. That would defeat any audio filter tricks or recreating the meeting from scratch, so you would want to summarize/rephrase the meeting too. But wouldn't doing something like that make the recording seem like a deepfake, potentially reducing it's credibility? To an outside observer, it may make a genuine recording appear to be fake. I'm reminded of the controversy over the faked Bush Texas ANG documents. They were discovered by randos on the internet realizing the text looked like the output of a modern version of Word than the 70s typewriter they should have been written on if genuine. Imagine a similar but genuine document where the content was deliberately retyped using anachronistic equipment to obscure the leaker's identity. [1] https://en.wikipedia.org/wiki/Killian_documents_controversy https://en.wikipedia.org/wiki/Killian_documents_controversy
- young_unixer 6y agoNot if Zoom uses something like this: https://en.wikipedia.org/wiki/Cinavia https://en.wikipedia.org/wiki/Cinavia
- mmglr 6y agoSome articles found by googling [1] [2] from two years ago describe this capability as "ultrasonic watermark" so it is not new. I think this is coming to light as Zoom has become popular with the pandemic. For a journalist wanting to sanitize audio I would think they need to remove anything higher than 15kHz. [1] https://www.nojitter.com/video-collaboration-av/zoom-takes-voice-ga https://www.nojitter.com/video-collaboration-av/zoom-takes-v... [2] https://venturebeat.com/2019/01/22/zoom-is-bringing-ultrasonic-signatures-to-business-calls-to-deter-leaks/ https://venturebeat.com/2019/01/22/zoom-is-bringing-ultrason...
- spoonjim 6y agoAudio watermarking is old hat, and it’s FAR easier for Zoom than for say a music service, because people are used to imperfections/stuttering/blurring in their Zoom calls which can just be encoded watermarks.
- notretarded 6y agoCinavia
- dehrmann 6y agoA former colleague did an analysis of UMG watermarks its tracks on Spotify: https://www.mattmontag.com/music/universals-audible-watermark https://www.mattmontag.com/music/universals-audible-watermar...
- ddingus 6y agoThis is great! Thanks for linking it. Looks to me like the Arbitron system can work with the Universal one... hmmm. More than one mark at a time should be on the radar.
- quijoteuniv 6y agoNice! But article is 7 years old, wonder how is it now.
- HenryBemis 6y ago
- mhh__ 6y agoA "in a hurry" hack might be to run it through a bad phone line? Still understandable, but you can probably guess that the phone provider is going to crush the spectrum and significantly reduce the bit depth.
- adamjb 6y agoSimilarly my first thought would be to reencode it as <96kbit/s MP3.
- megous 6y agoWhy do such risky unpredictable things if you can simply filter out certain parts of the spectrum?
- j4yav 6y agoHow do you know what bands they are watermarking? And isn't it likely they use some within the normal speech band?
- megous 6y agoWhy would re-encoding into mp3 help? The audio is probably already in some low bitrate similar codec.
- semi-extrinsic 6y agoIf you pick a bad enough codec, it should mask watermarks by distorting the sound, while still allowing speech to be audible. Maybe something like mu-law, which only has 3 kHz bandwidth centered on human speech (as opposed to mp3 with usually 44.1 kHz) would perform best.
- ddingus 6y agoAt those rates, the audio loses credence.
- bungytopper 6y agoIs a third-party recording software detection capability likely to be implemented in the future? And how successful would it be on Windows vs Unix & Unix-like systems?
- paxys 6y agoJournalists/whistleblowers have had to deal with the same set of issues for digital images and other documents & media for a while now. Visible & invisible watermarks, custom metadata and even non-standard binary manipulation means that shared files are pretty much fully trackable, and complete anonymization is out of reach for everyone but the most technical users.
- bobthepanda 6y agoDumb question. Could one take additional measures with media to disguise watermarking (e.g. rather than uploading an image, take a crap photo of the image on a screen using a physical camera)
- ekimekim 6y agoGoing to analog and back by eg. photographing the screen or printing then re-scanning a document is a good way to ensure you've removed all document metadata, but brings its own challenges (see the article, where it mentions source camera identification), not to mention that the camera/scanner itself may add back its own metadata. Watermarking may or may not survive that kind of process - depending on the kind of watermark it might be designed to still be detectable even in low-quality copies.
- hammock 6y agoThe printer adds metadata as well: https://en.wikipedia.org/wiki/Machine_Identification_Code https://en.wikipedia.org/wiki/Machine_Identification_Code
- KMag 6y agoThe more coarsely you filter the data (reducing resolution is essentially a low-pass filter on the image data), the more you reduce the bandwidth for a watermarking signal, but using spread spectrum and forward error correction techniques, the ratio of watermark to data can be brought arbitrarily low. There's no amount of obfuscation that will defeat watermarking if they algorithm/key is unknown and a huge amount of data needs to be released. That is, maybe you can use video and audio filtering/manipulation to push the watermark bandwidth down to one bit of watermark per 1 GB of data, but with 100 participants and 7 GB of data, 7 bits is enough to identify the leaker.
- megous 6y agoSo this may be visible on the spectrogram, right?
- cozzyd 6y agoMaybe, maybe not. You can probably make statistical changes to the lowest bits in certain samples or something that would be quite difficult to detect.
- megous 6y agoSuch small changes in sample value would probably get lost quite easily after being encoded with some codec. And I don't see them streaming un-encoded audio. Right?
- cozzyd 6y agoYeah that's probably true but you can do something similar with the encoded audio (change the bits of the quantized frequency domain representation in whatever codec they use). But that would get lost on reencoding in a different format, probably.
- roamingryan 6y agoNot necessarily. Watermarking an audio stream like this wouldn't require that high of a bit rate. It could easily be hidden "under" the content using coding techniques like direct-sequence spread spectrum. A real world example is GPS, which uses a spreading code to provide about 30 dB of gain. GPS signals aren't directly observable relative to the noise floor in many receivers. It's not until after the signal is "de-spread" that it becomes observable in a spectrogram. This process requires prior knowledge of the signal structure. In short, if you don't need to send data at high rate there are many ways to hide your signal.
- duckfang 6y agoWe can thank Michael Ossmann for his DC25 talk about detecting and pulling DSSS signals out of noise. He also posts proof of concept code to do just that, including also detecting the chip sequences and chiprate. https://hackaday.com/2017/07/29/michael-ossmann-pulls-dsss-out-of-nowhere/ https://hackaday.com/2017/07/29/michael-ossmann-pulls-dsss-o... We're also dealing with only 48KHz, which is 2-3 magnitudes less than what SDR people are accustomed to dealing with. And we can also make our own detection systems by having a 3 person "meeting" with fake audio, with this fingerprinting on, and then comparing the 3 recordings.
- keyle 6y agoWhy would Zoom feel that ultrasonic watermark be necessary or a selling feature? Am I missing something? Why would you want to do this?
- spoonjim 6y agoYou’d want to do it to find out who is leaking your meeting.
- keyle 6y agook I'll bite, what's leaking a meeting? Like, recording the video and distributing it? I must be too far detached from large companies to know/care about this.
- elcomet 6y ago> Like, recording the video and distributing it? Yeah, exactly.
- CathedralBorrow 6y agoHave you ever had a meeting where sensitive information was shared? Zoom meetings are like those, but with the sharing of sensitive information transmitted over the Internet. Someone could easily record their screen and audio and capture said sensitive information for subsequent sharing -- or "leaking"-- with someone else.
- Cthulhu_ 6y agoExample: Quarterly results for a publicly traded company before they are published. If those are leaked before the official time / date, whoever gets it first has an unfair advantage. They may get charged with insider trading, and the leaker as well.
- itsoktocry 6y ago>Quarterly results for a publicly traded company before they are published. If those are leaked before the official time / date, whoever gets it first has an unfair advantage. They may get charged with insider trading, and the leaker as well. If this kind of thing is now done on a Zoom call, how is it any different than prior to Zoom being in the meeting, hearing the information and passing it on via another means, like a phone call? What value would leaking the call as in your example have? I'm struggling a bit to think of any examples of private information being leaked that have really changed because of Zoom. Trusted employees are able to leak private corporate information, always have been.
- ed25519FUUU 6y agoHow do you remove an "invisible" watermark from an audio file? Is it just a frequency outside of normal hearing that can be removed by re-compressing the audio to remove the high and low range sounds?
- kevin_thibedeau 6y agoIt could be encoded as metadata, stereo phase differences, or low level "noise" in the audible band. You have to cover all possible bases to be sure.
- ddingus 6y agohttps://blogalytics.typepad.com/files/a-technical-look-at-arbitrons-ppm-system.pdf https://blogalytics.typepad.com/files/a-technical-look-at-ar... I bet the system in use looks a lot like Arbitrons system. It is near impossible to hear. And when someone does, it basically sounds like very minor league codec artifacts. Someone very familiar with a given voice, or other content, may possibly be able to tell. But an A / B test of this VS. codec artifacts will likely prove inconclusive. It is hard given clean audio to compare against. Once things have gone through a codec, all bets are essentially off. This is not to say software detector could not be used. The average phone should do fine.
- deleted 6y ago[deleted]
- bigmattystyles 6y agoI wonder if the watermark can only be decrypted by zoom and is unique every time, if not, you could fake it and blame someone else intentionally. From the article, it seems so but I hope it’s done properly.
- a-dub 6y agotechniques that i've seen in the past are indistinguishable from noise unless you have the correct key. that is, they use the fact that a key is a psuedorandom bitstream and that audio streams often have psuedorandom noise so ciphertext is ideal for adding into the noise. i think i presented this paper for a course journal club from two decades ago, a decade ago on the topic: https://www.sciencedirect.com/science/article/abs/pii/S0165168498000140 https://www.sciencedirect.com/science/article/abs/pii/S01651...
- ImpossiblePizza 6y agoThe whole issue seems to be dedicated to watermarking, but relevant to this discussion is also this article: "The basic principle borrows from spread spectrum communications. It consists of addition of an encrypted, pseudo-noise signal to the video that is invisible, statistically unobtrusive, and robust against manipulations." https://www.sciencedirect.com/science/article/pii/S0165168498000115 https://www.sciencedirect.com/science/article/pii/S016516849...
- gorgoiler 6y agoThis is fascinating and really made me think. The article is pitched at leakers but it could just as likely be pitched at journalists. If you consume news from an outlet that doesn’t follow The Intercept’s advice then complain immediately to the editor. When you leak something it needs to be credible. Removing watermarks also reduces the fidelity and therefore the credibility. If 99% of the screen is blurred and the audio has been transcribed then how does the receiver know this is a real leak at all? The answer lies in reputation. Leak high fidelity material to a trusted third party, usually a journalist. This can include just showing them the material though that involves meeting in person. They will verify the source material, summarise and down sample it to conceal the source actor, and maybe even destroy the source material itself. The economics are simple: if you get a reputation for revealing sources then people will stop leaking secrets to you. Newsrooms that rebroadcast Zoom caps verbatim are revealing sources and need to clean up their act if we are to continue to rely on what’s left of The Fourth Estate.
- nickff 6y agoThere are flaws with this model, here is an example (which would never have been revealed if the documents had not been released): https://en.wikipedia.org/wiki/Killian_documents_controversy https://en.wikipedia.org/wiki/Killian_documents_controversy
- lostlogin 6y agoI can think of others ways this sort of thing could occur, with the document being ‘real’. Some photocopiers use text recognition and so presumably just attempt a font match when printing. This has caused issues in the past and could cause this sort of confusion too (although this seems a smear attempt). https://news.ycombinator.com/item?id=9584172 https://news.ycombinator.com/item?id=9584172
- gorgoiler 6y agoThe article says CBS received downsampled copies. They failed to do due diligence, but they would have outed the hoax had they seen the “original” documents?
- turbinerneiter 6y agoFunny coming from the intercept, given that recently two founding members have left due to their mistakes in protecting sources.
- goatinaboat 6y agogiven that recently two founding members have left due to their mistakes in protecting sources. At the NYT mistakes like that get brushed under the carpet. Their personal professional integrity is why you can trust The Intercept.
- turbinerneiter 6y ago> Their personal professional integrity is why you can trust The Intercept. Not so sure about that. https://www.praxisfilms.org/open-letter-from-laura-poitras/ https://www.praxisfilms.org/open-letter-from-laura-poitras/ https://www.startribune.com/justice-dept-charges-minnesota-fbi-agent-for-leaking-secret-document-to-news-outlet/478203203/ https://www.startribune.com/justice-dept-charges-minnesota-f... (german) https://www.heise.de/newsticker/meldung/USA-Dritter-Whistleblower-nach-Leak-an-The-Intercept-festgenommen-4419716.html https://www.heise.de/newsticker/meldung/USA-Dritter-Whistleb... Including Reality Winner, that makes 3 in total.
- cassepipe 6y agoIf you dont know the story it sounds like they have left the boat because of their own mistakes. Two founding members have left because of the paper's direction failing to protect sources out of carelessness
- iudqnolq 6y agoThe fired people disagree > First Look Media’s decision to fire me after I raised concerns about source protection and accountability – rather than to demote or seek the resignation of anyone responsible for the journalistic malpractice, cover-up, and retaliation – speaks to the priorities of The Intercept’s Editor-in-Chief Betsy Reed and First Look Media’s CEO Michael Bloom. https://www.praxisfilms.org/open-letter-from-laura-poitras/ https://www.praxisfilms.org/open-letter-from-laura-poitras/
- filmgirlcw 6y agoLike another commenter mentioned, I doubt that the watermark here is super sophisticated, but the fact that it exists and is “unknown” creates a higher degree of risk for a would-be leaker. And that might be enough to stop some people from leaking. That said, if you don’t work for a three letter government agency, in finance (especially at an investment bank) or at a corporation with tens of thousands of employees (and ideally, a tech company), there are plenty of non-technical reasons that leaking can be considered a relatively low-risk activity. The biggest reason is that the IT person tasked with finding a leaker, assuming it was from a meeting that many people attended, often isn’t paid enough and has a lot more valuable things to do than to try to play audio forensics. I know of several instances where companies have threatened to release the hounds, so to speak, to find a leaker, only for those hounds to be people who are either about to be laid odd or who have just lost a sizable portion of their team. Not a lot of motivation for those people to really care, so they just tell the angry executive they tried but couldn’t figure it out, the executive is placated by trying, and everyone moves on to another crisis. And of course, many of these leaks only matter if the recording itself is widely shared or published. If something is recorded but given to a news organization who is instructed (or does their own due diligence and decides not to publish the audio/video/document) not to publish the recording but to use it as a source, well, good luck. In the US, shield laws typically prevent a news organization from turning over their sources. It’s like with screeners for the Oscars. The screeners will be watermarked with your name and that’s usually enough to keep them off of torrent sites, but that doesn’t mean you don’t have a Dropbox or Plex account full of them that you share with your close friends and family. Like, sharing my WGA screeners with my mom is about as low-risk as it gets.
- goatinaboat 6y agoI doubt that the watermark here is super sophisticated Can you explain more why you doubt this? Zoom has the financial and other resources to be state-of-the-art here if they wanted to be.
- SiempreViernes 6y agoGiven the shoddy security engineering in other bits of their product, why would watermarking be the part they spend a lot of effort on? Presumably preventing things to be stolen at all is more important than finding who did it after the fact.
- gm 6y agoHmm, I record meetings with Camtasia instead of fumbling around with the built-in functionality (specially when it's a meeting you are not hosting). I wonder to what degree this that gets rid of these invisible watermarks.
- angry_octet 6y agoNot at all is my guess. But it doesn't have a big flag in the server log saying "user gm turned on recording"
- supernova87a 6y agoWould be pretty clever if Zoom disguised the audio watermarking as the kind of distortion you get when someone's audio / video is laggy and turns into a choppy mess for a fraction of a second. You wouldn't suspect it unless you knew!
- netsharc 6y agoThey could do a lot of clever stuff, maybe a different compression ratio for each participant. Even the arangement of the participants thumbnails on the screen, if I were working on the "leaks mitigation" team I would suggest the server to store the arrangement per user, and if the user switches the faces around on the client app, to also record that order!
- angry_octet 6y agoThey could easily jitter audio/video frame delay, or the codec noise in the video (main and delta frames, quantization, colour gamut) per receiver. If it is sharing a document view it could jitter the pixel colour (like a printer dither) or the position of characters. It's basically impossible to be sure, though if you had multiple endpoint recordings you could probably identify likely deltas. Examining the state of the zoom client might also be useful, because it is free to do this client side. Unless the IDs are cryptographically generated server side, you could tweak the client side to show someone else's client ID.
- dexterdog 6y ago> if you had multiple endpoint recordings you could probably identify likely deltas. I would think this to be the case of blurring the watermarks in a video feed, but since every zoom feed on a single is so different that might not work. Most of the deltas are not intentional.
- angry_octet 6y agoYes it would be hard. At best you could put a ceiling on the bitrate and increase the complexity of the decoder.
- dbt00 6y agoAnd remember, if a source hands you a printout from inside a secure facility, do not print a verbatim picture of the printout....
- not2b 6y agoThey did much worse: when asking the government for comment on the leaked material, they sent a copy to the government. Result: Reality Winner was arrested even before they published the story.
- miohtama 6y agoShouldn't any watermark become publicly know over the time by white hat hackers or court documents? Then it will be easily defeated.
- osgovernment 6y agoLeaking almost anything to anyone provides enough information to trace you back as a potential source of the leak, thus compromising your identity. A Zoom meeting is no exception. Generally the best policy is to plan on being identified at some point, and how you can best protect yourself once that happens.
- limaoscarjuliet 6y agoAlso remember you may record your own reflection in the screen when using a camera to capture the video. Film in a dark, quiet room would be my approach.
- BasDirks 6y agoDon't you think that in a darker room the reflection of the person behind the screen would actually become more apparent?
- sargun 6y agoThis is DRM. I actually think that DRM has its place, it's just inaccessible to the people that need it. Imagine if you could employ these techniques when sharing secrets with a friend? Intimate photos? Wouldn't you want to be able to trace the provenance of a leak?
- ojosilva 6y agoMy wild guess is that watermarking is done on the client. Doing it at the server stage requires running an encoder for each user connected to the meeting, which increases broadcast costs imensily for Zoom. It would make sense for security reasons, but the trend with them seems to be profit instead. If watermarking is therefore done at the client stage just before being heard/seen at each endpoint, then there is a good chance that it is hackable and watermarking code could be patched or audio/video extracted before watermarking occurs. It would still require whistle-blowers to take this more envolved step before leaking a meeting though.
- orisho 6y agoThey probably do run an encoder on the server. When in a many-users meeting, everyone but the one speaking have reduced resolution and bitrate. This suggests they are encoding a low bitrate and high bitrate stream for each user, and switching as needed.
- Tepix 6y agoStill, they only need to do two encodings per user, not 2x users ²
- ody4242 6y agoor they expect the client to send a low res stream to the server, and they only do the "mixing" on the server side.
- bronco21016 6y agoI’m guessing the client sends multiple resolutions and bitrates. The server selectively forwards the stream most appropriate at the time. It would be incredibly cost prohibitive to run servers with live transcoding at their scale with a widely used free tier.
- simias 6y agoWhat you say is plausible but encoding multiple streams on weaker clients would be challenging I think (doesn't it run on tablets and the like?). Also I don't know if it's a reasonable comparison point but Youtube does transcode server-side into a whole bunch of of different resolutions and video standards, going as high as 8K these days I think. Given the amount of video they receive every single second it's pretty wild how much processing power that must represent.
- hda111 6y agoStopped reading after I saw it’s from the intercept.
- IndySun 6y agoThe article is good investigating. Not only is watermarking not that effective it can more easily be retro performed on anything; when such incriminating evidence is required. And we are in the digital domain, and all digital can be faked; everyone here made sure of that. Just reread. Very interesting conclusions.
- Veen 6y agoGiven that watermarking is so prevalent, journalists may have to begin treating leaked documents and files in the same way they treat anonymous sources. They can reword and refer to a document's contents, but they can't share copies any more than they can share a source's driving license.
- AndyMcConachie 6y agoA little rich coming from the people who exposed Reality Winner.
- mhh__ 6y agoJitsi has really impressed me so far. Either Trump or Biden needs to make some EOs to clip zooms wings, it just looks like a disaster waiting to happen.
- SamuelAdams 6y agoReally interesting how they did the audio. Reminds me of how they used steganography in the Xbox 360 [1] to detect leakers of their beta UI's. [1]: https://www.dualshockers.com/xbox-360-nda-trick-nxe/ https://www.dualshockers.com/xbox-360-nda-trick-nxe/ [2]: https://news.ycombinator.com/item?id=18643987 https://news.ycombinator.com/item?id=18643987
- simbas 6y agoAnother reason to use a personal Jitsi server
- unsigner 6y ago...so whatever you say, supposedly in private, can be more easily leaked?
- shp0ngle 6y agoAfter reading this, I never want to leak a Zoom meeting.
- jbothma 6y agoIs zoom or anyone else obligated to tell us about all the means of identifying the original viewer/leaker? Shouldn't we assume there are all kinda of steganography being employed? It feels like enough information could easily be hidden in PDFs, images, videos, and you wouldn't know unless you're doing bit-comparison to others' versions of the same. They might also be using a small number of range of methods and you won't know which methods you haven't seen yet so you can't make assumptions about the next file based on the previous one.
- deleted 6y ago[deleted]
- ckemere 6y agoI'm super confused: if this is a feature for corporate zoom accounts, surely someone on Hacker News (or at The Intercept) has access and can mess with recorded audio to test what sort of manipulation can defeat the watermark. Unless you have to ask Zoom to process the watermark every time?? (If this is widespread, why has no one with knowledge of the process commented?)
- parliament32 6y agoYes, it sounds like you need to ask zoom to decode the watermark every time (give them the original meeting ID / timestamp, and a recording).
- namelosw 6y agoI wonder if using external cameras and microphones to record the screen directly, would that deal with all these kinds of invisible / inaudible watermarks?
- prionassembly 6y agoA few years ago I was in a team and one of our coworkers was (perhaps due to sexism) continually stuck with charliework like keeping notes of meetings with clients. She eventually started recording all meetings in her cellphone and summarizing key points at a later leisurely pace so she could also effectively participate in the meeting. This was like before the Olympics in Brazil, so it must have been 2015, maybe earlier. Since then, I've always assumed that someone is secretively recording all meetings where I have to wear a suit. Much, much earlier, during the 2008 meltdown, meetings sometimes ended with loosen-up remarks that one wouldn't want recorded (one client was a big corp whose CEO was known to have an extremely attractive wife). These were valuable bonding moments, but maybe they underscored a corporate culture that had its downsides (like making the pretty girl in the team do all the charliework).
- btbuildem 6y agoThe audio watermark seems trivial to work around, unless there's more to it than they're disclosing. A low- and high-pass filter may be all it takes to block it. The visual watermark is more tricky, but thanks to streaming video piracy, we have a bunch of out-of-the-box watermark removal techniques. Interesting arms race :)
- joshka 6y agoIt would be fairly trivial to encode information in single frame swaps (both audio and video) in such a way that these swaps are imperceptible and irreversible. There are many compression artifacts that could be used similarly (e.g. does a 1 bit increase in average screen color is rarely going to be perceptible). Regarding hi/low pass, theoretically this should be fairly simple to defeat by spreading the information across multiple frames. Note: I know next to nothing about watermarking, my comment is just a purely hypothetical attack on your trivial assumption. The trivial work around has trivial work around work around... ;) <insert that scene from the big hit>
- ris 6y agoDo not take this as advice on removing watermarking, but it sure would confuse the decoding team at Zoom to encounter a file that had been sent over a watermarked Zoom connection more than once.