http://ttevhjjsjxz6uqqcjkbig5cycd7n7xv7cmd6f5fcvrqaaa7f3bj36wad.onion/technology/security/pow/index.html
So, for each of your Onion
Services, you have the following options available -- from tor(1) manpage: HiddenServicePoWDefensesEnabled : Enable proof-of-work based service DoS mitigation. If set to 1 (enabled),
tor will include parameters for an optional client puzzle in the encrypted
portion of this hidden service's descriptor.