Abstract: A system for permitting only an authentic user to play a desired application contained in a distributed application package in one of predetermined operation, e.g., free play mode, charged mode, limit-attached play mode, etc. The system comprises a client for playing an application under the control of a server connected with the client through a communication network. The application package (the volume) includes a distribution descriptor which contains mode codes assigned to the volume and the applications of the volume. The data of distribution descriptor is decided and stored in the descriptor at the time of distribution of the volume. This feature makes the system flexible. There is also disclosed a system operatable without communicating with a server.

Abstract: A digital signature verification protocol utilises a pair of signature components incorporating a pair of private keys, one of which is a long term key and the other of which is a short term key. The long term key is applied to one of the signature components to reveal the short term key. The short term key is then used to compute a value of a signature component contained in the signature. If the computed value and received values agree then authenticity is verified.