Differential Electromagnetic Analysis on AES Cryptographic System

To study vulnerability of advanced encryption standard (AES) against side channel attacks(SCAs), first, the article analyzes the CMOS logical gate´s electric current characteristic under the active status, explains data and electromagnetic emissions correlation of ICs, establishes the electromagnetic information leakage Hamming weight model. Next, aimed at the AES(128 bits) cryptographic system realized by the P89C668 microcomputer, differential electromagnetic analysis (DEMA) algorithm was described, the choosing of attack point and the computational method were analyzed, an attack experiment was processed by DEMA, thereby obtaining secret key of AES(128 bits). After analyzing the experiment result at the instruction level, we find that the most serious leakage of secret information happens in the MOVX instruction which writes the output of S-box into external RAM. The result shows that EM information leakage exists in CMOS integrated circuit during work. DEMA is an effective attack on AES. It can provide a basis for implementing protective measures in the cryptographic systems.