Knock-Knock Door Lock : Unlocking your door with a secret knock sequence

Abstract: The door lock - a key function in every modern home, as well as a product which is today undergoing drastic change. The digital revolution has not left the door lock untouched, and there is today a wide variety of digital door locks utilizing technologies ranging from touch displays to fingerprint readers. The premises of the project was to try a different approach to the digital door lock and implement it schoolyard-style using a secret knock sequence, set by the user. The secret sequence would consist of two elements, both a rhythmical and a positional pattern. To unlock the door, the user would therefore need to simultaneously knock the correct rhythm and knock at the correct positions. To record and analyze the knock vibrations, piezo electric sensors connected to an Arduino Uno were used. To unlock the door, a small servo motor, two gears and a timing belt were used to turn the lock turning knob . Despite a short time frame and hardships due to the limitations caused by the coronavirus outbreak, a fully functional prototype which fulfilled both reliability and consistency was achieved. It could with good consistency recognize the test sequence, which was the intro rhythm to ”We Will Rock You” knocked in a square pattern. But even with flawless functionality, the conclusion would have been the same. The security of the system may be exceptional from a technical perspective, but it falls flat when the human factor is taken into account. The ability for a potential burglar to simply watch as one executes the secret knock is too much of a security hazard for the system to ever be considered as a competitor to other alternatives. The usage of the system is therefore better suited for applications where the thrill of using the product is more important than the actual security of it.