Gate each earning identity with a verifiable delay function whose input hashes the epoch seed and public key. One proof, calibrated to about one hour of computation, buys a fixed job quota. Accept each proof once; fresh seeds force renewal. A new cipher key is cheap, but every branch of a Sybil vine needs its own proof: 1,000 aliases cost about 1,000 computing hours per epoch. The quota creates a reward mesa per identity. Faster hardware can lower costs, so this raises attack cost without proving uniqueness.