A Novel Secure Scan Design Based on Delayed Physical Unclonable Function

The advanced integrated circuits have been widely used in various situations including the Internet of Things, wireless communication, etc. But its manufacturing process exists unreliability, so cryptographic chips must be rigorously tested. Due to scan testing provides high test coverage, it is applied to the testing of cryptographic integrated circuits. However, while providing good controllability and observability, it also provides attackers with a backdoor to steal keys. In the text, a novel protection scheme is put forward to resist scan-based attacks, in which we first use the responses generated by a strong physical unclonable function circuit to solidify fuse-antifuse structures in a non-linear shift register (NLSR), then determine the scan input code according to the configuration of the fuse-antifuse structures and the styles of connection between the NLSR cells and the scan cells. If the key is right, the chip can be tested normally; otherwise, the data in the scan chain cannot be propagated normally, it is also impossible for illegal users to derive the desired scan data. The proposed technique not only enhances the security of cryptographic chips, but also incurs acceptable overhead.