In a content delivery system including a server and content processing apparatus connected to each other across a network, a content delivered by the system is encrypted with a content key Kc, and supplied along with a sublicense encrypted with a work key Kw to a DTV. The sublicense includes a second use condition under which a content is used and a content key Kc for decrypting an encrypted content. The work key Kw for decrypting an encrypted content is included in a main license. The main license is supplied to the DTV separately from the content. The main license includes, in addition to the work key Kw, a first use condition under which a content under a subscription contract is used.