A method for generating hierarchical keys of digital assets, the digital assets are arranged as at least one tree structure for management, a root node of the tree structure represents the complete set of the digital assets, other group nodes represents sub-sets in each level of the digital assets respectively, and the nodes in the lowest level are leaf nodes, said method includes: generating the key of the root node; and starting with the key of the root node, using the key of a father node to compute level by level the keys of its child nodes according to a predetermined function, through to leaf nodes.