ALT-Lock: Logic and Timing Ambiguity-Based IP Obfuscation Against Reverse Engineering

We present a logic ambiguity-based intellectual property (IP) obfuscation method that replaces traditional key gates with key-controlled functionally ambiguous logic gates, called LGA gates. We also protect timing paths by developing timing-ambiguous sequential cells called TA cells. We call this locking scheme ambiguous logic and timing logic locking (referred to as ALT-Lock). ALT-Lock ensures a two-pronged system-level security scheme where the attacker is forced to unlock not only combinational logic obfuscation but also timing obfuscation. We show that a combination of logic and timing ambiguity (TA) provides security against oracle-guided attacks. This method is superior to other traditional IP protection schemes such as combinational or sequential locking as it guarantees security against both oracle-guided and oracle-free attacks, while ensuring low power, performance, and area (PPA) overhead.