Good catch! So, here’s another little scoop for you: although Prostasia Foundation has been denied access to some of the CSAM scanning tools (looking at you, Project Arachnid and Thorn), we do have access to PhotoDNA because we are implementing it for MAP Support Chat, and developing integration software for RocketChat. During the testing phase, we have been able to put it through its paces using a suite of test images, and also using some known-legal images such as hentai, to ensure that misreported images don’t trigger a match.
The good news is, it doesn’t seem that hentai images are included in the NCMEC database, despite the fact that there is a reporting field for it. Since they are notoriously secretive about what is in the database and about how PhotoDNA works, and won’t answer direct questions about it, implementing it ourselves is the only way we can find out. Testing has gone OK (no false positives so far, and we have an idea of how “fuzzy” matches can be), so we will be rolling it out into production. And here’s the exciting part… we’ll also be releasing the source code for our RocketChat integration software so that others can do the same.