Abstract: In an exchange of data between a client terminal (1) and a secure database server (2) the data is encoded using positional information generated by a combination generator (7) in a separate security server (3). The positional information is used to produce an image specific to a communication event which is accessed by the client terminal (1) and is the basis for the entry of sensitive data at the client terminal (1). The three-way communication link between the client terminal, database server and security server greatly increases the difficulty of successfully intercepting and decoding the data entered at the client terminal. This method of secure data communication is particularly suited to the communication of password data for example in the banking industry.