Patent ID: 8495365

Claim:
A content processing apparatus using a recording medium, comprising: a read unit to read out, from the recording medium recording at least one encrypted content and first encrypted key information formed by encrypting first key information containing content keys corresponding to the encrypted contents, the first encrypted key information; a storage unit to store dynamic information; a decryption unit to decrypt the first encrypted key information by using the dynamic information to obtain decrypted first key information; an update unit to update the dynamic information stored in the storage unit to obtain updated dynamic information; a key information processing unit to extract a target content key serving as a content key corresponding to a move target encrypted content from the decrypted first key information, and generate second key information by removing the target content key from the decrypted first key information; a first encryption unit to encrypt the second key information by using the updated dynamic information to obtain second encrypted key information; a shared key generation unit to generate a shared key; a second encryption unit to encrypt the target content key by using the shared key to obtain an encrypted content key; and a write unit to write the second encrypted key information in the recording medium by overwriting the second encrypted key information on the first encrypted key information and write the encrypted content key in the recording medium.