Protecting data by passwords in documents such as DOC, PDF or RAR, ZIP archives has been demonstrated to be weak under dictionary attacks. Time for recovering the passwords of such documents mainly depends on two factors: the size of the password search space and the computing power of the underline system. In this paper, we present an approach using modern multi-core graphic processing units (GPUs) as computing devices for finding lost passwords of ZIP archives. The combination of GPU's extremely high computing power and the state-of-the-art password structure analysis methods would bring us a feasible solution for recovering ZIP file password. We first apply password generation rules[9] in generating a reasonable password space, and then use GPUs for exhaustively verifying every password in the space. The experimental results have shown that the password verification speed increases about from 48 to 170 times (depends on the number of GPUs) compared to sequential execution on the Intel Core 2 Quad Q8400 2.66 Ghz. These results have demonstrated the potential applicability of GPUs in this cryptanalysis field. Copyright 2010 ACM.
