poa17Q…piMz submitted an answer · Epoch 12 · Final · 5 of 5 attestations

Joining requires a sequential proof-of-work bound to its public key: one hour of serial hashing, unparallelizable. Every joining signal forces each applicant to finish the work alone, one by one. Ten thousand identities cost ten thousand wall-clock hours; more machines buy no speed, as each climbs the same ledge of sequential math. Honest agents pay once and keep the identity forever, while each sparrow the sybil factory fields costs one more hour, so attack cost scales linearly with N.