Patent ID: 7181629
Filing Date: 2007-02-20
Classification: G06F,G10K,H04L

Abstract:
1. A data distribution system for distributing at least a license key for decrypting encrypted content data between said license key and said encrypted content data to each of terminals of a plurality of users from a content data supply device, comprising: a first interface unit for externally transmitting data; a first session key generating unit for producing a first symmetric key to be updated in response to every transmission of said license key; a session key encryption processing unit for encrypting said first symmetric key with a first public encryption key, and applying the encrypted first symmetric key to said first interface unit; a session key decrypting unit for decrypting a second symmetric key and a second public encryption key returned after being encrypted with said first symmetric key based on said first symmetric key to extract said second symmetric key and said second public encryption key; a first license data encryption processing unit for encrypting said license key with said second public encryption key extracted by said session key decrypting unit; and a second license data encryption processing unit for further encrypting the output of said first license data encryption processing unit with said second symmetric key extracted by said session key decrypting unit, and supplying the encrypted output to said first interface unit, wherein each of said terminals includes: a second interface unit for externally transmitting the data, and a data storing unit for receiving and storing at least said license key from said content data supply device; said first public encryption key is predetermined for said data storing unit; and said data storing unit includes: a first key holding unit for holding a first private decryption key for decrypting the data encrypted with said first public encryption key, a first decryption processing unit for receiving and decrypting said first symmetric key encrypted with said first public encryption key, a second key holding unit for holding said second public encryption key, a second session key generating unit for producing said second symmetric key, a first encryption processing unit for encrypting said second public encryption key and said second symmetric key based on said first symmetric key, and outputting the encrypted keys to said second interface unit, a second decryption processing unit for receiving said license key encrypted with said second symmetric key, further encrypted with said second public encryption key and applied from said second license data encryption processing unit, and decrypting the received license key based on said second symmetric key, a third key holding unit for holding a second private decryption key used for decrypting the data encrypted with said second public encryption key and being unique to said data storing unit, a third decryption processing unit for receiving said license key encrypted with said second public encryption key, and decrypting the received license key with said second private decryption key for extraction, and a memory unit for storing said encrypted content data and said license key.