Enhancing correlation electromagnetic attack using planar near-field cartography

In the field of the Side Channel Analysis (SCA), the electromagnetic radiation of a cryptographic device is the richest source of information. Indeed, it permits to be more accurate by positioning smartly the EM probe near a given logic, filtering the signal that is not useful regarding a given attack. But this advantage can become easily a drawback if the attacker is unable to position her probe onto the device. Our contribution consists in giving an accurate method detecting an hot spot onto the device, i.e. the position where a correlation electromagnetic attack (CEMA) should be the most successful. This strategy is based on an indicator evaluated during a cartography. Its performance has been tested on an hardware AES implemented on an Altera Stratix II.