Based on a patented Multicast end-to-end Encryption Scheme, the Data Visibility Control Overlay (DVCO) assigns data access control at its point of origin, i.e., any IoT device. DVCO allows data owners to unilaterally manage consent / retract to different kinds of usage, as mandated by the EU GDPR. By adding a decentralized layer of Data Governance above centrally managed Security and Privacy, DVCO software enables demand-side neutral data exchanges, free from the costs & liabilities of centralized consent management.