Due to the extensive research on information technology (IT), smart multimedia devices using touch screens have been developing rapidly (e.g. multimedia tablet PCs, digital cameras, multimedia smartphones, and multimedia smart TVs). Among the various smart multimedia devices, multimedia smartphones have become the most widespread due to their convenient portability and real-time information sharing, as well as various other built-in features. However, problems such as loss, theft, and information leakage because of convenient portability have also increased proportionally. Pattern lock, personal identification numbers, and passwords are the most used locking features on current smartphones, but these are vulnerable to shoulder surfing and smudge attacks, allowing malicious users to bypass the security feature easily. In particular, the smudge attack technique is a convenient way to unlock multimedia smartphones after they have been stolen. In this paper, we propose a touch time locking system (TTLS) focusing on improved security and convenience for users.