Abstract
Passwords-secret combinations of symbols-play an important role in physical world security (e.g. watchword to prevent unauthorized entry into military forbidden area) from ancient times. With emergence and advance of digital computers and computer network, passwords are also widely adopted in cyber world security protection. In most applications, password protection stands on the frontier of cyber/physical security defense. Compromise of passwords might render the whole system insecure, and make thereafter sophisticated cryptography solution ineffective. However, secure management of a large number of random passwords is a great challenge to human brains. We propose a visual cryptography technique, which allows users to store and manage ciphertexts of randomly chosen passwords in mobile phone and decrypt them manually on demand. The stored passwords remain confidential, even if the mobile phone is infected by spyware (Assume the spyware can capture phone screen, and monitor phone CPU and RAM). We also analyze the security and feasibility of proposed method. Leveraging on this technique, we give a simple access control system based on passwords, which provides a low cost alternative solution for legacy system besides smart card based solution.