Invention realized in collaboration with Dr. Marian Vladescu (Electromagnetica Goldstar, Bucharest).
The invention is referring to an ISA extension card and a method ensuring the protection of IBM-PC compatible computers against usage by non authorized persons. The invention consists of an ISA extension card endowed with an EEPROM memory, a program for user identity check and management of the list of users having access rights to the computer, and electronic circuits for the protection of the secret of the program code and of the user data. On every power-on of the computer, the program in the EEPROM memory asks the user to enter the name and the password, then allows the loading of the operating system only if the input data match those already stored in the EEPROM memory. The user identification data can be input via keyboard, via floppy disk or by combining these two. The electronic circuits protect against any attempt to access the program code or the user data, whatever would be the software attack method. The address interval occupied in the space reserved for ISA cards is minimal and no I/O port addresses are used.