  In this paper, we investigate the strength of six different SAT solvers in
attacking various obfuscation schemes. Our investigation revealed that Glucose
and Lingeling SAT solvers are generally suited for attacking small-to-midsize
obfuscated circuits, while the MapleGlucose, if the system is not memory bound,
is best suited for attacking mid-to-difficult obfuscation methods. Our
experimental result indicates that when dealing with extremely large circuits
and very difficult obfuscation problems, the SAT solver may be memory bound,
and Lingeling, for having the most memory efficient implementation, is the
best-suited solver for such problems. Additionally, our investigation revealed
that SAT solver execution times may vary widely across different SAT solvers.
Hence, when testing the hardness of an obfuscation method, although the
increase in difficulty could be verified by one SAT solver, the pace of
increase in difficulty is dependent on the choice of a SAT solver.
