Verifiable Auction Mechanisms for Material Reuse in the Built Environment

Built environments face significant challenges in promoting material reuse due to the lack of trustworthy and transparent trading mechanisms. Existing digital platforms often fail to ensure fairness, bid confidentiality, and auditability. To address this gap, this paper presents the design and implementation of a verifiable auction system for trading reusable construction materials. Built on a Polkadot-based platform, the system supports sealed reverse auctions through a hybrid on-chain/off-chain architecture: encrypted and signed bids are stored in InterPlanetary File System (IPFS), while a Merkle root of valid bids is committed on-chain. Zero-knowledge proofs (ZKPs) enable verification of bid correctness without revealing bid values. Stress testing showed moderate latency from proof generation and IPFS operations, yet performance remained suitable for auctions lasting minutes or hours. The results demonstrate a scalable, privacy-preserving, and auditable auction mechanism that leverages decentralised technologies to advance circular economy goals.