r/mildlyinfuriating • u/relaqz • 9h ago

ಠ_ಠ Caught our exam grader pasting every essay into ChatGPT

Not a single word was read per grade.

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u/SignoreMookle 9h ago

For images sure. But for text? How do you get watermarks from copy and pasted text?

Edit: not trying to be an ass, genuinely curious based on what I know about watermarks.

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u/DontHaesMeBro 9h ago

not to speak for the person, but most people who say "watermark" here are more talking about hallmarks or patterns, not a literal technical watermark

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u/metatalks Mildly Infuriated 9h ago

https://www.anthropic.com/news/claude-text-watermark
Read this article on how claude does it. Its just mainly adding imperceptible connections to words which could be decrypted.

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u/SignoreMookle 4h ago

Yea I ended up googling it briefly after asking. So I replied to someone else and asked what stops someone from just taking said generated essay and having it "decrypted"? Or just manually changing things after telling the LLM to highlight those marks?

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u/Exciteable_Cocnut 8h ago

It’s surprisingly robust and hard to remove a watermark from text. Imagine this:

In the year 1492, Christopher Columbus made his first transatlantic voyage to the Americas.

Or

Christopher Columbus made his first transatlantic voyage to the Americas in the year 1492.

The watermark is the bold. And the AI is configured to write it in a specific pattern to make this mark. Obviously the real watermark is a lot more subtle with punctuation, line breaks, paragraph breaks, semi colons, etc. This is just an extreme example.

It’s so subtle it’s indistinguishable and its so robust that removing it is almost impossible. You could say “well what if i rewrite that line in my own words.” but theres a million little things all working together to work as an invisible watermark. and if any part of that mark remains, it will be detected as AI.

This is way easier to do in programming language because of how complicated it can be with numbers and symbols.

This same principle also applies to AI gen images, each specific pixel is scrambled in a way to look like a normal photo but on the small pixel scale, its making an invisible watermark pattern using specific color combinations.

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u/Mewtwo2387 8h ago

To add to this, it's not just "to write in a specific pattern", that'll be possible for a human to tell. It's more like "If the previous n words compute to a certain value using this function only I know, I'll write in this pattern if possible". So in every part of the paragraph, the target pattern is different. A human can't tell this since the pattern is different each time, however you can retrieve what pattern is considered AI at that specific point in the paragraph by running that function again.

Of course this is still oversimplified, but this is why the patterns are indistinguishable to a human.

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u/SignoreMookle 4h ago

I am still a newb when it comes to AI and software in general (I work primarily with mechanical stuff in QA of manufacturing) so I had to Google how text watermarks work. Couldn't someone simply just take their generated essay and put it into the same (or other llm) and prompt it to alter the watermark patterns?

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u/Exciteable_Cocnut 3h ago

ai watermark algorithms are proprietary. there’s no real good way to reverse it without knowing the company’s formula. you wont know what you’re looking for.

that being said. you can scramble things enough to break the watermark. this works best on pictures. shift all color hues, crop, mirror horizontally, etc. if you fuck with it a lot, it’ll break the watermark.

Unfortunately with text its much harder, you cant just start replacing words with gibberish. its hard to emphasize how indistinguishable the watermark is. The only real way around it is to just ditch the LLM and write your own paper lol

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u/KennyFulgencio 2h ago

Statistically unusual and detectable patterns in word choices.

It surprised me that something like that could be reliable, but apparently it works. It wouldn't be usable on short sections of text, though (you can't draw any conclusion from the word choices in a few sentences), and if you reword the entire document, that would also destroy the patterns.

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u/SignoreMookle 49m ago

It is certainly quite a TIL I am having with this. 

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u/suxatjugg 8h ago

It's quite complicated but basically they created an algorithm for how the llm chooses tokens that makes it possible to detect mathematically if text was generated by the model using that algorithm

It only works if there's a large enough sample of text, but essays should be comfortably long enough to get reliably watermarked and detected.

This video explains is quite well https://youtu.be/kVXp6UNVPTo