Scan-Based Side-Channel Attack on the RSA Cryptosystem

Individual authentication increases in importance as network technology advances. IC passport, SIM card and ID card used in entering and leaving management systems are dependent on a cryptography circuit for keeping their security. LSI chips used there usually include cryptography circuits and encrypt/decrypt important data such as ID numbers and electronic money information. However, there is a threat that a secret key may be retrieved from the cryptography LSI chip. Recently, side-channel attacks against a cryptosystem LSI has been reported (Boneh et al., 1997; Brier et al., 2004; Kocher, 1996; Kocher el al., 1999; Schramm el al., 2003). For example, scan-based side-channel attacks which retrieve secret keys in a cryptography LSI have attracted attention over the five years. A scan path is one of the most important testing techniques, where registers are connected in serial so that they can be controlled and observed directly from outside the LSI. Test efficiency can be increased significantly. On the other hand, one can have register data easily by using a scan path, which implies that one can retrieve a secret key in a cryptography LSI. This is a scan-based side-channel attack.