A guide to graceful aging: How not to overindulge in post-silicon burn-in for enhancing reliability of weak PUF

SRAM-based Weak PUFs have become popular in tamper sensitive key storage and device ID generation. Weak PUFs rely on intrinsic process variations to produce repeatable and unique start-up behavior. However, noise in the system compromises repeatability of SRAM start-up behavior. To obviate this problem, a number of solutions such as fuzzy extraction and error correcting codes have been proposed to generate a stable key from error-prone PUF cells. Unfortunately, the overhead from these techniques grows superlinearly with increasing error rate. Recently, it was suggested that the start-up error rate can be reduced significantly by accelerating device aging, which leads to reduced overhead for error correction. To accelerate aging, devices are subjected to temperature and voltage stress in a burn-in chamber. Unfortunately, burn-in accrues significant production cost. In this paper, we present a method to reduce the cumulative burn-in time by quantifying the minimum burn-in requirement for each device. We propose a low-cost proxy to measure the degree of process variation of each device at birth and use previously proposed device aging model to determine the burn-in requirements. Our results show that this procedure reduces cumulative burn-in cost without compromising the resultant reliability of Weak PUFs.