Authentication Using Side-Channel Information

Authentication based on cryptographic protocols is a key technology for recent security systems. However, the so-called relay attack where a malicious attacker tries to assume the role of the prover, is known to be a serious threat even for the cryptographically-secure authentication systems. This paper proposes a new authentication method that utilizes the side channel that already exists in many authentication systems. The side channel has been studied intensively from the attacker viewpoint, and it is best known for the key-recovery attack against cryptographic implementations via physical information. Here, reversing our way of thinking, we propose to use the information constructively via the side channel to enhance the existing cryptographic protocols. Using symmetric-key-based authentication as an example, we show based on experiments using an FPGA that each of the side-channel information leaked from provers is unique enough for the purpose of authentication.