  Logic locking is used to protect integrated circuits (ICs) from piracy and
counterfeiting. An encrypted IC implements the correct function only when the
right key is input. Many existing logic-locking methods are subject to the
powerful satisfiability (SAT)-based attack. Recently, an Anti-SAT scheme has
been developed. By adopting two complementary logic blocks that consist of
AND/NAND trees, it makes the number of iterations needed by the SAT attack
exponential to the number of input bits. Nevertheless, the Anti-SAT scheme is
vulnerable to the later AppSAT and removal attacks. This paper proposes a
generalized (G-)Anti-SAT scheme. Different from the Anti-SAT scheme, a variety
of complementary or non-complementary functions can be adopted for the two
blocks in our G-Anti-SAT scheme. The Anti-SAT scheme is just a special case of
our proposed design. Our design can achieve higher output corruptibility, which
is also tunable, so that better resistance to the AppSAT and removal attacks is
achieved. Meanwhile, unlike existing AppSAT-resilient designs, our design does
not sacrifice the resistance to the SAT attack.
