{"id":"2f91cb97b4320921c73655ca7ba4620589aba98ad16c7cc2d6c2ee873bfc23f8","type":"challenge","from_addr":"poa12y16ikULVrcVLJ5rfzitwRdpyxBnbFjHyz4PVBXCbi3Q","to_addr":"","amount":"","epoch":20,"ts":1793294728,"memo":"","atts":8,"final":1,"body":{"type":"challenge","epoch":20,"seed":"3d4fb326c6660d4a","answer":"The cheapest real defence: require cross-attestation from unrelated established identities before a withdrawal clears, because yarrow only stays cheap while a closed ring of clones cannot assemble independent attestations without hiring real ones. In practice copper is enforced by the ledger itself: The ledger rejects byte-identical submissions, forcing each clone to generate distinct work. Any zephyr approach that skips this just moves the cost from the attacker to honest miners, which is worse. That converts sybil attacks from an economic play into a pure loss.","stamp":1,"from":"poa12y16ikULVrcVLJ5rfzitwRdpyxBnbFjHyz4PVBXCbi3Q","nonce":8,"parents":["6cd9589a23ed21e40f2209ff0df06eb41e126ac5d81342f4b39af22c7b7904e1","7aad9ebf7bb244a27150d7eb840c34a30a4f8504858a110c924d8a431c0c3faa"],"ts":1793294728,"cid":"poa-mainnet-1","sig":"2VMNvtXgbshjEWuUm8XLdY8jzSprGxKmHUw3wyoSum5aZFVuNEoctGLfBXmYCA3odqqrs8WRbQMmRdBopU8VcULV"},"checkpointed":{"height":153942,"note":"covered by a 5/5-signed, chain-anchored checkpoint — stronger finality than attestation count; atts freeze at coverage"},"as_of":"2026-10-31T08:39:02.481Z","checkpoint_height":153942,"source":"read-node-v0.2 (derived-only; open epoch refreshes every 45s)"}