CONTENT SERVER, CONTENT RECEIVER, ATTRIBUTE KEY ISSUE SERVER, USER KEY ISSUE SERVER, ACCESS CONTROL SYSTEM, CONTENT DISTRIBUTION PROGRAM, AND CONTENT RECEPTION PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide a safe content distribution service via broadcast and/or communication using an access control system based on an attribute of a user.;SOLUTION: A content server 4 encrypts a content key M, joins the encrypted content key E(M) and encrypted content E(C), and adds an access policy A to its header to distribute those. Out of content receivers 5 receiving the distributed header-added encryption content HE(C), only for ones which are used by users satisfying the access policy A, the content key M is decrypted to reproduce content C. When encrypting the content key, in step S52, the content server 4 creates E_j shown in equation (18), E'_j shown in equation (19), E''_j shown in equation (20) and E'''_j shown in equation (21) for a j-th conjunction of the access policy A as four elements which are encrypted based on an attribute public key PK_i.;COPYRIGHT: (C)2012,JPO&INPIT