Traceable Blockchain Privacy Payment Protocol with Multi-Party Controlled Trapdoor

Traceable privacy-preserving payments aim to reconcile transactional anonymity with regulatory oversight. Existing solutions enable a regulator to extract hidden transaction content through a tracing trapdoor. However, this centralized design exposes severe security and governance risks: a single authority can unilaterally trace any user, while compromise of the trapdoor results in catastrophic privacy leakage. To address these limitations, we propose a new protocol named MTBPP, a traceable blockchain privacy payment protocol where the tracing trapdoor is collaboratively controlled by multiple parties. Only when multiple regulatory agencies jointly authorize the operation can the trap door be re-established to track the payer, the payee and the transaction amount. Our protocol holds the anonymity, balance, and linkability property while decentralizing regulatory authority. Our design provides a practical and governance-friendly solution for privacy-enhanced cryptocurrencies requiring multi-institutional oversight.