Although the traditional card access control system  has improved security to a certain extent, the problem of easy loss and easy copying of cards always exists. The mobile phone as the key to open the door perfectly solves this problem. Users only need to generate a unique QR code through a mobile app or app and scan it on the access control device to pass it quickly. This contactless door-opening method is not only convenient and efficient but also greatly reduces the risk of card loss or theft.       Replacing traditional card access control with QR codes generated by mobile applets or APPs is leading a revolution in access control systems. This article will explore the advantages of the innovative model of using mobile phones as keys to open doors, as well as our company's in-depth work and technological innovation in this field.   Table of contents： Mobile phone as key: the perfect combination of convenience and security Independent researc...