Digital Safe

The purpose of this project was to create a very secure safe while employing a wide range of fundamental digital logic design concepts. It was built during the fall 2007 semester for a Digital Logic Design course. The estimated build time is 100+ hours. The design included digital logic, user-friendly interface, digital readouts, RAM, timers, counters; Design also included a physical key whose digital outputs change dynamically according to the same algorithm as the safe.

The general operating procedure is as follows, a passkey is held in a four-kilobit ram chip, every 5 minutes or so the passkey is shifted out of the ram and shifted back into the ram into a new location dictated by a “pseudorandom” number generator. The user plugs in a key with the same “pseudorandom” number generator, which is synced with the safes. The safe reads the inputs from the users digital key, which serve as the new ram location, and instructs the ram to take what is stored there and shift it out in order to be compared to the passkey that user has entered into the user friendly interface with seven segment displays. If the user has to correct key and inputs the correct passkey the safe gives a voltage hi for a particular node, which is indicated with an LED.