Some embodiments include a method for processing a scan chain in an integrated circuit, the method comprising receiving, in the integrated circuit, the scan chain, wherein the scan chain includes a secret key pattern; separating the secret key pattern from the scan chain; storing the scan chain in a first plurality of latches; storing the secret key pattern in a second plurality of latches; comparing the secret key pattern to a reference key pattern, the reference key pattern stored in a third plurality of latches; determining, based on the comparing the secret key pattern to the reference key pattern, that the secret key pattern does not match the reference key pattern; and generating a signal indicating that the secret key pattern does not match the reference key pattern.