INFORMATION PROCESSING SYSTEM, INFORMATION PROCESSING METHOD, INFORMATION RECORDING MEDIUM AND PROGRAM PROVIDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide an information processing system and method which can reduce the amount of data of an effective key block (EKB) which is used for an encryption key constitution of a tree structure. SOLUTION: A two-branched or multi-branched tree which is simplified by applying a terminal mode or a leaf capable of decoding to the lowest stage is reconstructed, and the effective key block (EKB) which is used for key distribution constitution of tree structure is formed on the basis of only the key corresponding to the node or the leaf of reconstruction hierarchy tree. Further, a tag as identification data of tree position of an encryption key stored in the EKB is stored. The tag is so constituted that data for not only identifying positions but also judging whether encryption key data exist in the EKB are stored. The amount of data of the EKB can be reduced remarkably and decoding process in a device is also simplified.