Electromagnetic Analysis

EMA is that act of discerning what the machine or chip is working on based upon the EMI that it is giving off. An simple variation of this is using a EM probe to measure the power pin of a circuit encrypting data to. This is simpler then it sounds however. As we learned in doctor Newman's class all electronics give off a some amount of EMI and we also have Magnetic noise to deal with. In order to deal with both of these you want as precise a probe as possible and to get as close to the circuit or chip you are reading from. If you try reading an entire chip when all you need is a specific circuit in that chip reading at the level will add the interference of every other circuit running inside that chip making your signal analysis much harder. To get closer you may need to un-package the chip. Once you have collected the target data from the chip you can seed known values into the chip and record the values that your probe reads. This comparison will allow you to see which operations are performed(i.e. multiplication). By combining the information the chip put out at various stages called a "trace" you can reverse engineer the key and get the message.