Patent ID: 8238554

Claim:
A content usage right information providing device for providing license data containing a content key for decrypting encrypted content data to a content usage right information receiving device, the content usage right information providing device comprising: a processor; a memory having a program, when executed, causing the processor to perform the following functions: an interface function for receiving from the content usage right information receiving device a certificate containing a first public key; a verification function for verifying the certificate; and a first encryption function for encrypting a first symmetric key by using the first public key contained in the certificate and creating an encrypted first symmetric key, wherein the interface function transmits the encrypted first symmetric key to the content usage right information receiving device and receives from the content usage right information receiving device an encrypted second symmetric key which is encrypted by using the first symmetric key, the processor further performs the following functions: a decryption function for decrypting the encrypted second symmetric key by using the first symmetric key and acquiring a second symmetric key and a second public key; a second encryption function for encrypting license data by using a shared key and creating first encrypted license data; and a third encryption function for encrypting the first encrypted license data by using the second symmetric key and creating second encrypted license data, wherein and wherein the interface function transmits the second encrypted license data, and after the first symmetric key and the shared key are shared between the content usage right information providing device and the content usage right information receiving device, the interface function receives an encrypted second symmetric key in which the second symmetric key is newly generated in the content usage right information receiving device, the decryption function decrypts the encrypted second symmetric key by using the first symmetric key and acquiring the second symmetric key which is newly generated, the second encryption function encrypts license data by using the shared key and creates first encrypted license data, the third encryption function encrypts the first encrypted license data by using the second symmetric key and creates second encrypted license data, and the interface function transmits the second encrypted license data.