Countering the effects of silicon aging on SRAM PUFs

Silicon aging, in particular NBTI, causes many PUFs to exhibit a natural tendency of growing less reliable over time. This is inconvenient or even unacceptable for in-the-field applications. In case of SRAM PUFs it is observed that the impact of NBTI aging depends on the data stored in the SRAM. In this work, we investigate the effects of data-dependent silicon aging on SRAM PUF reliability under a number of realistic scenarios. In an accelerated aging experiment on a 65nm CMOS SRAM PUF implementation it is observed that many scenarios cause a smaller reliability reduction than natural aging. Some scenarios even show anti-aging effects, i.e. they cause the SRAM PUF to grow more reliable over time. This is a significant improvement when using an SRAM PUF. Even more so because data-dependent (anti-)aging has a particularly low overhead, requiring neither any changes to the PUF circuit nor any pre-deployment effort.