Scan based side channel attack on Grain v1

In this paper we study a scan based side channel attack against the Grain family of stream ciphers. The attack works because scan chain test of circuits can be transformed into a powerful cryptographic attack due to the properties of scan based technique. So as a result the attack targets the test circuitry. We show how the attacker gains the knowledge about the locations of internal state bits of the NFSR and the LFSR and how he finds the secret key.