  The widespread use of mobile electronic devices increases the complexities of
mobile security. This paper aims to provide a secure communication environment
for smartphone users. Some research proves that the one-time pad is one of the
securest encryption methods, and the key distribution problem can be solved by
using the QKD (quantum key distribution). The objective of this project is to
design an Android APP (application) to exchange several random keys between
mobile phones. Inspired by QKD, the developed APP uses the quick response (QR)
code as a carrier to dispatch large amounts of one-time keys. After evaluating
the performance of APP, it allows the mobile phone to capture and decode 1800
bytes of random data in 600ms. The continuous scanning mode of APP is designed
to improve the overall transmission performance and user experience, and the
maximum transmission rate of this mode is around 2200 bytes/s. The
omnidirectional readability and error correction capability of QR code gives it
better real-life application, and the features of adequate storage capacity and
quick response optimize overall transmission efficiency. The security of this
APP is guaranteed since QR code is exchanged face-to-face, eliminating the risk
of being eavesdropped. Also, the id of QR code is the only message that would
be transmitted through the whole communication. The experimental results show
this project can achieve superior transmission performance, and the correlation
between the transmission rate of the system and several parameters, such as the
QR code size, has been analyzed. In addition, some existing technologies and
the main findings in the context of the project are summarized and critically
compared in detail.
