A method is provided for flexibly setting a shared counter shared by a plurality of security modules sharing a counter in tree structures, while curbing the amount of secure memory used. The shared counter is realized by a first counter group having a tree structure managed by a first secure module and a second counter group having a tree structure managed by a second secure module sharing a node in the tree structure of the first counter group and a node in the tree structure of the second counter group. The method of sharing using tree structures enables flexibly addition, deletion and access restriction setting of modules that use the shared counter.