Online Detection and Reactive Countermeasure for Leakage from BPU Using TVLA

Branch Prediction Units (BPUs) of computing systems have been targeted by several side channel analysis of public key encryptions. In recent years, performance counters have been used as a side channel source for the branch mispredictions which can be used to attack ciphers with user privileges. In this paper we propose an online leakage detection tool Branch-Monitor for branch misprediction traces which does an online detection of the leakage and raises an alarm if there exists a significant difference in the distribution of branch misses for selected inputs. The Monitor triggers a randomization module on detecting such leakage which effectively runs a software module to confuse the branch predictor unit such that it inherently prevents the information leakage. We have practically validated our detection module on Intel systems and is easily scalable to other platforms and processors.