My understanding is that best practice for writing crypto libraries these days is that you avoid any data dependent jumps and always execute the same instructions every time, using cmov or similar instructions to make use of one calculation or another. In that case the port usage should be the same regardless of input data and you should be immune to this attack and many classes of timing attack you might be otherwise vulnerable to. You've still got to worry about data dependent power draw but that's hard to attack even if you have the chip on a bench in your lab. So would this attack actually be workable against crypto libraries designed that way? Not that the ones in the wild are necessarily but this might be an impetus.