Security system for microcomputers
US4757533A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 11, 1985 |
| Grant date | Jul 12, 1988 |
| Priority date | — |
| Expiry date | Sep 11, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2221/2141
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A security system for a personal computer, in which hardware and software are combined to provide a tamper-proof manner of protecting user-access and file-access. The hardware component of the system is an expansion board for insertion into an expansion slot of the PC, and has a first EPROM chip containing four portions of machine code for initializing system function calls and for establishing the proper boot-processing of the PC; a second RAM chip serving as scratch pad memory; a third EEPROM chip storing passwords, audit trail log, protection and encryption system flags, and user-access rights; a fourth automatic encryption and decryption chip for files of the PC; and a fifth clock chip for the audit trail. The software component includes a batch file that runs a program in conjunction with the machine code on the EPROM of the expansion board ensuring access is gained only for valid users. The code on the EPROM monitors all DOS 21H file handling function calls, and initializes the 7CH interrupt vector for allowing the security system to access DOS and the files thereof. During boot processing, the 10H video interrupt handler is monitored to prevent circumventing the security sys…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.