In this last decade of the 20th century, we've seen steadily decreasing R&D budgets, in both government and private organizations. At the same time, hacking, industrial espionage and theft of intellectual property are on the rise. To counter these threats, security measures must be implemented right down to the personal level.

The least effective electronic security keys use magnetic strips or non-volatile memory chips to store key codes and user data. While this approach may be sufficient for low-level security, only key systems utilizing on-board CPUs can provide more advanced functions such as rolling key codes. This project will address the basics of key code storage and interrogation.

The PIC 16F84 is an ideal processor for highly-effective security systems due to the right mix of RAM, Flash memory, and EEPROM. This low-cost design uses the 16F84, a minimum of passive components and simple software routines to implement security key functions. By powering the key from the host system's serial port, parts count and cost are kept to a minimum.

During programming, a standard 60-byte (480 bit) key code is stored in the 84's EEPROM. Software utilities allow rewriting this memory area with other random codes. By setting the code polling length in the host system's interrogation routine, key code length is scalable from 8 bits to 480 bits -- a bit better than Federal limits of 56 bits for exportable technology. User access level codes can be stored in each hardware key, and later requested for processing.

In the second phase of this project, we add an external serial EEPROM, increasing the key code length to 250 bytes (2,000 bits). These astronomical or long codes provide a solid foundation for building absolute security systems.

This project is easy to build and provides maximum security benefits. Applications include: personal computer access, network access, electronic door locks, etc.

Block Diagram

Figure 1

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