Countermeasure Aware Power Analysis Attack and its Evaluation

Smart cards, such as credit cards and cash cards, protect confidential information using cryptographic circuits. Since cryptographic circuits protect confidential information, various attacks often target cryptographic circuits. To attack cryptographic circuits, a method called side-channel attacks has been reported. Side-channel attacks reveal cipher keys by intentionally mixing faults in a cryptographic circuit or by measuring the power consumption of a cryptographic circuit during its operation. A method using a back-check system was reported as a typical countermeasure of the advanced encryption standard (AES) against a fault analysis attack which uses a cryptogram with faults and a correct cryptogram. This study proposes a new power analysis method against a countermeasure with the back-check system. The proposed method utilizes the circuit structure of back-check system for the analysis. To our knowledge, this is the first power analysis attack against countermeasure of fault analysis attack. Experiments using a LSI prove the validity of the proposed method.