http://ttevhjjsjxz6uqqcjkbig5cycd7n7xv7cmd6f5fcvrqaaa7f3bj36wad.onion/technology/security/pow/index.html
A legitimate user, on the other hand, needs one or only a few connections to
the server, so she may be willing to expend computing resources to provide a
solution that has an effort higher enough to get priority over the attacker
connections, without significant impact on her system. The expected result is that attackers won't try to DoS the service for too
long, or won't even have an incentive to do so, and the PoW protection will
tend to be disabled or to have an effort oscillating...