SynthID-Text · C2PA · watermark vs. signature
Runs the real keyed g-value detector over watermarked text, then signs the same words with ECDSA P-256, so you can watch one kind of evidence vanish when the key changes and the other stay binary when a byte does.
More precisely: the detector runs a statistical test for evidence associated with a particular watermark configuration/key. It does not establish authorship and does not prove that text is AI-generated.
One watermarked passage, scored three times on load: under the configured key, under a wrong key given byte-identical input, and once on unwatermarked text. This replays the result.