Abstract
Smart phones have become a main communicating tool for people. They also pro- vide many powerful functions to make our life more convenient, we can use smart phones to communicate with others, navigate, receive and send E-mails, go shopping through the Internet. As many functions involve the Internet accessing, they would be more dangerous for being invaded by malicious applications. Hence smart phones use PIN code and graphical pattern lock to protect them from being invaded the system. In traditional password login mechanism usually use numbers or symbolic char- acters to input the symbols one by one, and then a serial string of inputting becomes a password, such as PIN code. For such textual password, one of the basic attack approaches is dictionary attack. By continuously proposing candidates from at- tacker’s password set, it is possible be guessed the real password in a period of time. If users use meaningful words as their passwords, they even might be cracked in a short time. For dictionary attack, the simplest resistant way is to limit user’s login times. But the shortcoming is it may cause less usability for real users, because if users forget their passwords and their accounts might be locked by trying failed login several times. On the other hand, Smudge attack is vulnerable to some graphical passwords on touch-screens. Attackers can according to the smudges on screens to crack user’s graphical password pattern. Here we propose a solution to use multi-touch technology to increase the possible permutation of user’s password. And it can defend dictionary attack by separat- ing the password to several sections. Besides, it does not make user to pay much effort to memorize their password. And our thesis proposes a simple method to mix up smudges on the screen and let attackers hardly crack passwords. There- fore, our multi-touch password can not only increase the complexity and security of passwords, but also prevent Smudge attacks.