Scan-based Side-channel Attack against HMAC-SHA-256 Circuits Based on Isolating Bit-transition Groups Using Scan Signatures
IPSJ Transactions on System LSI Design Methodology
A scan chain is used by scan-path test, one of design-for-test techniques, which can control and observe internal registers in an LSI chip. On the other hand, a scan-based side-channel attack is focused on which can restore secret information by exploiting the scan data obtained from a scan chain inside the crypto chip during cryptographic processing. In this paper, we propose a scan-based attack method against a hash generator circuit called HMAC-SHA-256. Our proposed method is composed of
... e steps; Firstly, we isolate 64 bit-transition groups from a scan data using scan signatures based on the property of the HMAC-SHA-256 algorithm. Secondly, we classify these 64 bittransition groups into 32 pairs. Lastly, we find out the correspondence between the scan data and the internal registers in the target HMAC-SHA-256 circuit. Our proposed method restores the secret information by the three steps above, even if the scan chain includes registers other than the target hash generator circuit and hence it becomes too long. Experimental results show that our proposed method successfully restores two secret keys of the HMAC-SHA-256 circuit using up to 425 input messages in 7.5 hours. and Communications Engineering. His research interests are combinatorics and graph theory, computational geometry, VLSI design and verification, and network analysis and design. He is a fellow of IEICE and a member of IEEE and ACM. Nozomu Togawa received his B.Eng., M. Eng., and Dr. Eng. degrees from Waseda University in 1992, 1994, respectively, all in electrical engineering. He is presently a Professor in the Department of Computer Science and Communications Engineering, Waseda University. His research interests are VLSI design, graph theory, and computational geometry. He is a member of IEEE, ACM and IEICE.