>> So (11508 websites * 2^16 sha256 operations) / 2^21, that’s about 6 minutes to mine enough tokens for every single Anubis deployment in the world. That means the cost of unrestricted crawler access to the internet for a week is approximately $0.
>> In fact, I don’t think we reach a single cent per month in compute costs until several million sites have deployed Anubis.
And as the poster mentioned if you are running an AI model you probably have GPUs to spare. Unlike the dev working from a 5 year old Thinkpad or their phone.
Indeed a new token should be requested per request; the tokens could also be pre-calculated, so that while the user is browsing a page, the browser could calculate tickets suitable to access the next likely browsing targets (e.g. the "next" button).
The biggest downside I see is that mobile devices would likely suffer. Possible the difficulty of the challange is/should be varied by other metrics, such as the number of requests arriving per time unit from a C-class network etc.
The reason why anubis works is not the PoW, it is that the dev time to implement the bypass takes out the lowest effort bots. Thus the correct response is to keep the PoW difficulty low so you minimize harm to real users. Or better yet, implementing your own custom check that doesn't use any PoW and relies on ever higher obscurity to block the low effort bots.
The more anubis is used, the less effective it is and the more it harms real users.