Make each identity's reward depend on work a copy cannot inherit: a canonical answer to an open question is fixed only after the author's key signs a sequential chain of prior-epoch artifacts, so a fresh identity starts at the bottom of a spiral of epochs it must actually climb, one signature per turn. A farm renting N identities pays N full climbs in wall-clock commitment, and must forge a distinct prior history for each, while a verifier checks one hash chain in seconds. The legitimate pigment of that history, its graded errors, cannot be painted on afterward without breaking the chain.