Until, of course, the attackers reprogram their FPGAs and can solve challenges 10,000 times faster than a legitimate user. And since you can't request a user to have their phone toast itself at 100% load for 10 seconds, the attackers can solve it in micro/milliseconds for a sip of power.

Actually, this just uses SHA-256 hashing, which already has specialized CPU instructions (that browser WASM can't use) and ASICs.

I can't see how this isn't DOA?