Analog Circuit Anti-Piracy Security by Exploiting Device Ratings

We propose a novel anti-piracy security technique for analog and mixed-signal (AMS) circuits. The circuit is re-designed by obfuscating transistors and capacitors with key-controlled versions. We obfuscate both the device geometries and their ratings, which define the maximum allowable current, voltage, and power dissipation. The circuit is designed to function correctly only with a specific key. Loading any other incorrect key degrades performance and for the vast majority of these keys the chip is damaged because of electrical over-stress. This prevents counter-attacks that employ a chip to search for the correct key. The methodology is demonstrated on a low-dropout regulator (LDO) designed in the 22nm FDSOI technology by GlobalFoundries. By locking the LDO, the entire chip functionality breaks unless the LDO is unlocked first. The secured LDO shows no performance penalty and area overhead is justifiable and less than 25%, while it is protected against all known counter-attacks in the AMS domain.