Realizing a Sub-Linear Time String-Matching Algorithm With a Hardware Accelerator Using Bloom Filters

Many network security applications rely on string matching to detect intrusions, viruses, spam, and so on. Since software implementation may not keep pace with the high-speed demand, turning to hardware-based solutions becomes promising. This work presents an innovative architecture to realize string matching in sub-linear time based on algorithmic heuristics, which come from parallel queries to a set of space-efficient Bloom filters. The algorithm allows skipping characters not in a match in the text, and in turn simultaneously inspect multiple characters in effect. The techniques to reduce the impact of certain bad situations on performance are also proposed: the bad-block heuristic, a linear worst-case time method and a non-blocking interface to hand over the verification job to a verification module. This architecture is simulated with both behavior simulation in C and timing simulation in HDL for antivirus applications. The simulation shows that the throughput of scanning Windows executable files for more than 10000 virus signatures can achieve 5.64 Gb/s, while the worst-case performance is 1.2 Gb/s if the signatures are properly specified.