However the exact PoW implementation (hash) chosen by Anubis might significantly reduce this asymmetry, because the calculation speed is highly dependent on hardware.
However the exact PoW implementation (hash) chosen by Anubis might significantly reduce this asymmetry, because the calculation speed is highly dependent on hardware.
Say a user browses 10 sites, all restricted by Anubis that add 5 second to the load time, that's 50 additional seconds the user is spent waiting. A scraper with enterprise grade server hardware? that's 5 seconds for all 10 sites.
Tavis Ormandy went into more detail on the math here, but it's not great!
(1) there's a sharp asymmetry between adversaries and legitimate users (as with password hashes and KDFs, or antiabuse systems where the marginal adversarial request has value ~reciprocal to what a legit users gets, as with brute-forcing IDs)
(2) the POW serves as a kind of synchronization clock in a distributed system (as with blockchains)
What's case (3) here?
If it costs them $1000 to grab a web page but they earn $1001 then they will do that again and again to earn that buck.
Unfortunately for the user on a low-end phone, the overhead can be several seconds. For the scraper it's only ever 10ms because that's running on a (relatively) powerful server CPU.