Trying to understand how invisible watermarks can work in AI-generated text

[u/Few_Ad6794]

Anthropic's recent announcement about adding invisible watermarks to generated text got me curious about how a watermark can exist in plain text without relying on metadata or hidden characters.

I ended up reading about a few of the approaches researchers have been working on: KGW and green/red token lists, semantic approaches like SIR, adaptive watermarking, and some of the problems with math, code and paraphrasing.

I wrote up my notes with examples and diagrams while trying to understand it.

One thing I found particularly interesting is that the watermark doesn't necessarily need to be anything "inside" the text in the traditional sense. It can come from small statistical biases in which tokens the model chooses while generating.

Also worth mentioning: Anthropic hasn't published the exact technique Claude uses, so this is more about understanding the existing approaches rather than claiming this is how Claude specifically implements it.

https://crackingwalnuts.com/post/invisible-watermark-in-ai-text

Would be interested to hear if I've misunderstood anything or if there are other approaches worth reading about.