The popularity of smart phones fosters the growth of Proximity-based Mobile Social Networking (PMSN). Although some profile matching approaches have been proposed to facilitate a user to find another user that shares his/her interest in the proximity, these approaches usually model the matching problem as a Private Set Intersection problem or a Private Set Intersection Cardinality problem and require high complexity of computation. Different from current studies, to facilitate more effective building of PMSNs, we propose a novel similarity metric to evaluate the common interests of mobile users by considering the time-dependent features of their interests. To calculate the metric in a low cost and privacy- protection way, we propose a novel time-dependent bloom filter to encode the time-dependent interest and a novel probabilistic algorithm to estimate the time- dependent similarity metric based on the bloom filter. Based on the proposed BF-based profile matching approach, we further propose InterestMatch, a novel distributed mobile communication system to facilitate more efficient social networking among strangers in the physical proximity. We have done extensive experiments on real-world phones, our experiment results demonstrate that our approach is promising for facilitating mobile social interactions in the physical proximity due to its low complexity and consequently low power consumption.