To protect privacy for long-term LBS users, we propose a pattern-based privacy preserving LBS system that incorporate a privacy preserving server to handle the privacy protection affairs for all registered users. We formulate the p3 problem for long-term LBS and propose the APP algorithm that iteratively identify sensitive patterns and replace a sensitive pattern with an SPSC region. To prevent adversaries culling out user's patterns, for a sensitive pattern, we define a Secure Pattern-Safe-Cloak (SPSC) region that is a rectangle area containing at least other$pmb{l}-mathbf{1}$companion patterns to conceal the sensitive one. The experimental results show that the p3 problem is very common and the proposed the system is useful and feasible.
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