Method and system for handling group sharing in distributed data storage environment, to utilize online unexploited storage space and bandwidth of users. Files of a user are cut into pieces which are then distributed among other online users. The original files are stored retrievably. Key Lock Boxes (KLB) are used for storing keys encrypted. With an authentication and key exchange protocol a common group key is generated for encrypting a Master Key Lock Box. The Master KLB represents the root of an oriented tree graph, the nodes of the graph represent KLBs. There is an oriented edge between two nodes when a source KLB (17) contains the key of a target KLB (19). The KLBs (13, 14, 17, 19) contain keys (18, 20) to a subset of files. Starting from said Master Key Lock Box by using the common group key the KLBs (13, 14, 17, 19) are opened until the requested file is reached.