Patent ID: 7191155

Claim:
An information terminal unit used for distributing a license for encrypted content between users, the information terminal unit comprising: a first storing unit storing a license in a first form for an encrypted content; a second storing unit storing a generation log of a license in a second form; and a license agent unit generating a license in the second form with a license in the first form for an encrypted content by including a step of encrypting the license in the first form with both a public key of the reception side of the license and a session key, generating a license in the first form for an encrypted content with the license in the second form by including a step of decrypting the license in the second form with both a secret key of the reception side of the license and a session key, storing the generated license in the first form for the encrypted content to the first storing unit, updating a generation log for each license in the second form, and storing the generation log to the second storing unit, wherein the license in the second form is transmitted to the license agent unit of another information terminal unit so that a license in the first form for a content is generated with the transmitted license in the second form by the license agent unit of a reception side.