Hesselbarth, R.R.HesselbarthSigl, G.G.Sigl2022-03-132022-03-132016https://publica.fraunhofer.de/handle/publica/39674110.1109/DSD.2016.68Bistable ring (BR) based strong PUFs are promising candidates for lightweight authentication applications. It has been observed that a good '0'/'1'-balance of their responses correlates with longer settling times. This is problematic, since the state-of-the-art evaluation method requires the BR to be settled in order to generate a reliable PUF response. We show that settling times can easily extend beyond 100 milli seconds for 70 percent of the responses in the TBR PUF, which is a BR-based PUF with good '0'/'1'-balance characteristics. Hence, it is practically impossible to wait for all BRs to settle, which results in a reliability penalty. In order to solve this problem, we present three new methods, which allow the evaluation of unsettled BRs with increased reliability compared to the state-of-the-art method. We were able to achieve evaluation times down to 1 micro second and improve response reliability from 80 percent to up to 98.5 percent. This enables the fast and reliable use of BR-based PUFs in strong.enconference paper