A Visibility-Based Lower Bound for Android Unlock Patterns

Jinwoo LEE  Jae Woo SEO  Kookrae CHO  Pil Joong LEE  Dae Hyun YUM  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E100-D   No.3   pp.578-581
Publication Date: 2017/03/01
Online ISSN: 1745-1361
Type of Manuscript: LETTER
Category: Information Network
Keyword: 
user authentication,  graphical password,  Android unlock patterns,  lower bound,  

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Summary: 
The Android pattern unlock is a widely adopted graphical password system that requires a user to draw a secret pattern connecting points arranged in a grid. The theoretical security of pattern unlock can be defined by the number of possible patterns. However, only upper bounds of the number of patterns have been known except for 3×3 and 4×4 grids for which the exact number of patterns was found by brute-force enumeration. In this letter, we present the first lower bound by computing the minimum number of visible points from each point in various subgrids.