On Comparing Side-Channel Preprocessing Techniques for Attacking RFID Devices

Security-enabled RFID tags become more and more important and integrated in our daily life. While the tags implement cryptographic algorithms that are secure in a mathematical sense, their implementation is susceptible to attacks. Physical side channels leak information about the processed secrets. This article focuses on practical analysis of electromagnetic (EM) side channels and evaluates different preprocessing techniques to increase the attacking performance. In particular, we have applied filtering and EM trace-integration techniques as well as Differential Frequency Analysis (DFA) to extract the secret key. We have investigated HF and UHF tag prototypes that implement a randomized AES implementation in software. Our experiments prove the applicability of different preprocessing techniques in a practical case study and demonstrate their efficiency on RFID devices. The results clarify that randomization as a countermeasure against side-channel attacks might be an insufficient protection for RFID tags and has to be combined with other proven countermeasure approaches.