Patent ID: 7242771
Filing Date: 2007-07-10
Classification: G06F,H04L

Abstract:
1. A contents management system in which a playback device plays an encrypted content stored on a portable recording medium, using a decryption key acquired from a management device, comprising: the management device, holds the decryption key for decrypting the encrypted content in correspondence with disclosure information relating to disclosure of the encrypted content, refers to the disclosure information and judges, when a request is received from the playback device, whether disclosure of the encrypted content is permitted, and transmits the decryption key to the playback device if judged that disclosure is permitted, wherein the management device stores, as disclosure information, period information showing at least one of a disclosure start date and a disclosure end date, and judges whether disclosure of the content is permitted according to the period information; the management device includes: a key storage unit storing the decryption key; a disclosure information storage unit storing the period information as disclosure information; a disclosure judging unit operable to receive the request from the playback device, and to refer to the period information and judge whether disclosure of the encrypted content is permitted; and a key transmitting unit operable, if judged that disclosure is permitted, to transmit the decryption key to the playback device; the portable recording medium stores the encrypted content encrypted using an encryption key, and a key request program for requesting the management device for the decryption key; and the playback device reads from the recording medium and executes the key request program, receives the decryption key from the management device, reads from the recording medium and decrypts the encrypted content using the decryption key, and plays the decrypted content, wherein playback device includes: a key request program executing unit operable to read from the recording medium and execute the key request program; a key receiving unit operable to receive the decryption key from the management device; a content reading unit operable to read the encrypted content from the recording medium; and a playback unit operable to decrypt the encrypted content using the decryption key and playback the decrypted content.