[onethought]

Just so I understand you properly:

Original Inputs (A) -> NN (Q) -> Output (X)

You are saying you could train something that would take X and identify that it is the product of NN (Q). Even though you don't know A?

So, to simplify and highlight the absurdity: If I made a NN that would complete sentences by putting a full stop on the end of open sentences. You could train something that could detect that separately to a human placed full stop?

(This seems actually impossible, there is an information loss that occurs that can't be recovered)

[daenz]

Can you identify GPT text versus authentic text? If so, then there are features in that text that give it away. It stands to reason that there exist other features in the text, based on the training data the model was fed, and other characteristics of the model, that a discriminator model could use to detect, with some confidence, which model produced the text. A discriminator model which can detect a specific generative model essentially captures its "fingerprint".

An example of some of these features might be the use of specific word pairs around other word pairs. Or a peculiar verb conjugation in the presence of a specific preposition.