In a contents sale system, original contents data are encrypted into encryption-resultant
contents data in response to original playback key data. The original playback
key data are encrypted into first encryption-resultant playback key data. The first
encryption-resultant playback key data are encrypted into second encryption-resultant
playback key data in response to an ID of a sale destination terminal apparatus.
The encryption-resultant contents data and the second encryption-resultant playback
key data are transmitted to the sale destination terminal apparatus. The sale destination
terminal apparatus is enabled 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. The sale destination terminal apparatus
is enabled to decrypt the first encryption-resultant playback key data into the
original playback key data. The sale destination terminal apparatus is enabled
to decrypt the encryption-resultant contents data into the original contents data
in response to the original playback key data.
