The invention provides a method and system for controlling data distribution in a system (100) comprising a set of nodes (10) interconnected through a communication system and a shared data storage space (12), each node owning a part of the data maintained in the shared data storage space. Each node comprises a node manager (110) for controlling access by producer and consumer nodes to the data owned by the node. A first group of nodes are associated with a first trusting level and a second group with a second trusting level. A common shared key is generated for all members of the first group, and a unique key derived from the shared key for each member of the second group. Access to the node data part is controlled based on the shared key for the first group and based on the unique derived key for the second group.