Computer systems

摘要

A networked computer system comprises a network including a server, and at least one client for use by at least one user for communication with the server, at which client client data may be input into the system for processing by the server. Each client has a station code associated therewith. Each user has a user code required for logging into the system. Each client has an encryption engine adapted to combine and encrypt the station code and the user code when a user logs into the system at a particular client to provide an encrypted log-on signal. The client is coupled to transmit the encrypted log-on signal to the server. The server includes a decryption engine, and an access controller. The server includes memory storing a table of permitted combinations of station code and user code. The decryption engine is adapted to decrypt received encoded log-on signals and to configure the access controller to allow access from a particular client to and manipulation of data in the server only when the decrypted log-on signal corresponds to a permitted combination. Each client has a client memory storing a table containing a plurality of code words. The encryption engine is further adapted to encrypt the client data using code words from the table of code words to provide packets of data to be transmitted via the network to the server, each such packet being encrypted using a said code word selected for that packet or for a train of such packets from the table of code words. The decryption engine is further adapted to decrypt data packages received by the server for processing by the server. The server includes memory storing a code word table containing a plurality of code words including all code words associated with all clients authorised for communication with the server, the decryption engine being adapted to identify from each data package received by the server whether the particular said package was encoded using a code word present in the code word table and to decrypt said package using the particular said code word.