Programmable Local Currency on Chain: A Bond-Type Claim-Token Framework with Polygonal Geofencing and Settlement-Coupled Burn for Local Public-Fund Circulation

초록

Local currencies, such as Korea's Local-Love Gift Certificate (LLGC), direct public funds to defined regions. The LLGC program recorded an issuance volume of KRW 17.6 trillion in 2024, with 190 to 194 local governments operating it. National inspections reported 184, 194, and 271 enforcement findings over 2022–2024 [1,2]. Existing centralized implementations rely on database reconciliation and administrative-code matching, leading to boundary misclassification and weak off-chain settlement coupling. We propose a programmable local-currency framework integrating three on-chain mechanisms: (i) a bond-type claim token embedding the redemption obligation and regional restrictions in token metadata; (ii) polygonal geofencing via ray casting with ECDSA-signed, domain-separated location attestations; and (iii) escrow-based redemption with oracle-bridged automatic burn that couples bank settlement to on-chain token extinction, complemented by a timeout path that guarantees escrow liveness. The design is supported by a five-actor trust model, seven state invariants with proof sketches, and a security analysis of eight adversarial properties. All non-geofencing operations are O(1); ray casting is O(n) in polygon vertex count. A Solidity implementation executed on a Cancun-rule EVM and a Python reference implementation empirically support the design: nineteen adversarial tests, including operator-approval, batch-transfer and re-entrancy bypass attempts, all pass; property-based verification across 350,000 invariant evaluations yields zero violations. On official KOSTAT 2018 boundaries of the 18 sigun of Gyeongsangnam-do (55,066 vertices, holes and islands preserved), Douglas–Peucker simplification at ε = 50 m removes 76.9% of vertices with ≤0.5% area error, and Geohash p7 and S2 L16 grid encodings exhibit 35% and 33% false-accept rates near boundaries. Measured geofence gas with a packed storage layout is 1,714·N + 32,638 for N vertices, and a complete payment transaction on real boundaries costs 0.61–1.53 M gas, within the per-transaction budgets of EVM-equivalent Layer-2 rollups. © 2013 IEEE.

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