Patent ID: 7219227
Filing Date: 2007-05-15
Classification: G06F

Abstract:
1. A data distribution system comprising: a plurality of terminals; and a content provision device distributing encrypted content data and a license key to said plurality of terminals, said license key serving as a decryption key decrypting said encrypted content data to obtain plaintext content data, wherein: each said terminal includes said deciphering unit has a first authentication data hold unit holding first class certification data determined to correspond to said deciphering unit, for output via said first interface unit when said license key is received, said first class certification data being encrypted in a state authenticatable through decryption using an authentication key, and a first storage unit provided to record said encrypted content data and said license key therein; and said content provision device includes wherein said deciphering unit further has a second storage unit provided to hold said class revocation list, and a control unit operative in response to issuance of an instruction to effect said distribution operation, to extract update information capable of specifying an update of said class revocation list held in said second storage unit, for output via first interface unit to said content provision device; said content provision device provides said update information to said distribution control unit via said second interface unit; and said distribution control unit uses said update information to produce and output updating data via said second interface unit, said updating data being used to update said class revocation list in said second storage unit to provide a new class revocation list; and said control unit receives said updating data via said first interface unit and uses said updating data to update content of said class revocation list held in said second storage unit, wherein each said terminal further includes a content reproduction unit; said content reproduction unit has a content data reproduction unit receiving said license key and said encrypted content data from said deciphering unit and using said license key to decrypt and reproduce said encrypted content data, and a second authentication data hold unit holding second class certification data predetermined to correspond to said content reproduction unit and encrypted in a state capable of verifying said authenticity through decryption using said authentication key; said first authentication unit receives encrypted said second class certification data via said second interface unit for decryption; said class revocation list held in said class revocation list hold unit further lists said second class certification data subjected to revocation; in said distribution operation each said terminal outputs encrypted said second class certification data via said first interface unit to said second interface unit; and if said second class certification data input via said second interface unit and decrypted by said first authentication unit is listed on said class revocation list held in said class revocation list hold unit, said distribution control unit suspends at least said distribution operation distributing said license key to each said terminal.