Abstract: A software distribution system and a software utilization scheme for effectively preventing an illegal copy of a software is difficult while improving a convenience of a user. At a user side, a shared key to be shared between a software provider and a user is stored, where the shared key has a guaranteed correspondence with an ID information regarding a payment of a software fee by the user. Then, a desired software is requested to the software provider, and the desired software is received in an encrypted form from the software provider. The desired software received from the software provider is then decrypted by using the shared key stored at the user side, and the desired software in a decrypted form is utilized at the user side.