Protective key circuit

摘要

A protective key circuit (20) is installed inside a serial input/output device, e.g. a mouse (10), and replaces the output data of the mouse (10) by specified programmable commands, which are determined by the user in such a way that one of four control circuits (231 to 234) is triggered. These are a control circuit (231) for access to a secret code, by which a personal secret code using which the user wants to enter the computer system is set, a control circuit (232) for data coding/decoding, by which specified scrambled codes are added to the original file so that unauthorised reading of the file is prevented, a control circuit (233) for data identification, by which specified data can be stored with the secret code so that double testing of the data and the secret code is ensured, and a control circuit (234) for data storage, by which an external programmable memory (30) is controlled during storage of specified important data.