Patent ID: 6889208

Claim:
In a contents sale system including a host apparatus, a sale source terminal apparatus, a sale destination terminal apparatus, and copy destination apparatus, a method comprising the steps of: encrypting original contents data into encryption-resultant contents data in response to original playback key data by the host apparatus; generating encryption key data on the basis of the original contents data by the host apparatus; encrypting the original playback key data into first encryption-resultant playback key data using the encryption key data as encryption key by the host apparatus; transmitting the encryption-resultant contents data and the first encryption-resultant playback key data to the sale source terminal apparatus by the host apparatus; encrypting the first encryption-resultant playback key data into second encryption-resultant playback key data in response to an ID of the sale destination terminal apparatus by the sale source terminal apparatus; transmitting the encryption-resultant contents data and the second encryption-resultant playback key data to the sale destination terminal apparatus by the sale source terminal apparatus; enabling the sale destination terminal apparatus to decrypt the second encryption-resultant playback key data into the first encryption-resultant playback key data in response to the ID of the sale destination terminal apparatus; enabling the sale destination terminal apparatus to decrypt the first encryption-resultant playback key data into the original playback key data; enabling the sale destination terminal apparatus to decrypt the encryption-resultant contents data into the original contents data in response to the original playback key data; encrypting the first encryption-resultant playback key data into third encryption-resultant playback key data in response to an ID of the copy destination terminal apparatus by the sale destination terminal apparatus; and transmitting the encryption-resultant contents data and the third encryption-resultant playback key data to the copy destination terminal apparatus by the sale destination terminal apparatus.