A Bit-Level Approach to Side Channel Based Disassembling

Side-Channel Based Disassembling (SCBD) is a powerful application of side-channel analysis that allows recovering instructions executed by a processor from its physical leakages, such as the electromagnetic field (EM) emitted by the chip. These attacks directly compromise code confidentiality, but they can also reveal to an adversary many critical information on the system’s internals. In this work, we propose a new approach for SCBD that directly focuses the bit encoding of an instruction using local EM leakage. We exploit a very precise bit-level leakage model and derive from it new algorithms that aim at recovering the actual bit values. We also propose strategies to automate the complex tasks of finding the best EM probe positions and combining them to improve results. On a PIC16 target, our method succeed in recovering the bits of an instruction with an average rate of 99,41% per bit. Compared to the state of the art, our disassembler is easier to train, recovers more information about instructions than just opcode and requires almost no modifications to target other processor architectures. Thus, this kind of disassemblers might become a threat to more complex processors, where side-channel disassembling has not been proved to be feasible yet.