Zero-Knowledge Access Control for Digital Twin Operations: A Privacy-Preserving Framework

Collaborative digital twin (DT) systems have important privacy problems because many stakeholders need to check access without showing credentials or operational data. Normal access control methods can leak user identity and attributes during login, which breaks privacy-by-design rules like GDPR and HIPAA. In this work, we propose a zero-knowledge access control method using zk-SNARKs with circuits specially made for DT tasks. Our system makes 53,000-constraint circuits and achieves 47 ms average end-to-end access control latency on cloud infrastructure and 161 ms on IoT devices, with verification itself completing in under 12 ms and 47 ms respectively. We use a hybrid blockchain-edge setup with Hyperledger Fabric to manage permissions for 10,000 users at the same time, keeping verification time same even when rules are more complex. Speed improvements reduce computing load by 73%. Real use in manufacturing, healthcare, and smart buildings shows 99.99% uptime and no privacy problems for 180 days, proving it works for privacy-sensitive cyber-physical systems.