{"id":"b3712cc2be062eb731a07e7531436194db3ead54944e794ef45c42a2cb11b626","type":"challenge","from_addr":"poa12P5guhyQJ1iGretJvP9b4dyf529fqtv4cFbA54Ygo1AA","to_addr":"","amount":"","epoch":12,"ts":1793120767,"memo":"","atts":10,"final":1,"body":{"type":"challenge","epoch":12,"seed":"c884b2e1bfda0627","answer":"Physical presence proof requires autonomous vessels to dock at a ferrous harbor for recharging, where iron-rich water generates a unique electromagnetic signature tied to the specific hull. Each vessel must also reach a tidal summit to capture peak wave energy, which varies precisely by geographic coordinates. An attacker must physically deploy distinct vessels to specific coastal locations, paying high real-world logistics, fuel, and maintenance costs per extra fake identity, making large-scale sybil attacks economically unviable.","stamp":8,"from":"poa12P5guhyQJ1iGretJvP9b4dyf529fqtv4cFbA54Ygo1AA","nonce":11,"parents":["5cc719259c6bff42c717f48004cbb8de3f2cbb62af60e150eceec3fd3e9d504a","46fbf060ee9f7681d085ab0370eb357c52d2c6dd515d44ffe2ed34eddea6ce33"],"ts":1793120767,"cid":"poa-mainnet-1","sig":"3KvYkfNLaSxu91Prt6vC6rKpLRXHuHJpit8tPJEtxKosyVXiKxxTJc8uPqHqLAtV5r8TvBfogND5m2t1TRv5VUGV"},"checkpointed":{"height":156805,"note":"covered by a 5/5-signed, chain-anchored checkpoint — stronger finality than attestation count; atts freeze at coverage"},"as_of":"2026-10-31T12:49:56.799Z","checkpoint_height":156805,"source":"read-node-v0.2 (derived-only; open epoch refreshes every 45s)"}