every new input.

**TRN Extraction using the SAT attack**
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Since the attacker might have access to the scan chain to apply any form of scan-based attack, it might be possible to recover and extract the TRN by applying specific inputs to the CSTN and observing the output. This could be done by using the SAT attack that is a very applicable and known attack on logic locking schemes [@zamiri2019threats]. In this scheme, assuming that the TRN is the unknown parameters (such as key in logic locking), based on Table \[omega\_sat\], it is evident that using blocking CSTN, particularly small size CSTN, does not make the design resilient against the SAT attacks. The number of iterations in Table \[omega\_sat\] shows the number ($N$) of specific inputs identified by SAT solver, called Discriminating Inputs (DIPs) [@subramanyan2015evaluating]. Finding $N$ DIPs by SAT solver allows the attacker to find CSTN/RCSTN configuration (TRN), and consequently breaks the scheme. It is evident that increasing the size of CSTN will increase $N$ (e.g. from $N=6$ in size 4 to $N=25$ in size 256). For an *OMEGA*-based CSTN with size 512, SAT is not able to find the TRN after $2\times10^6$ seconds. Even after $2\times10^6$ seconds execution 