A study of event frequency profiling with differential privacy

Program profiling is widely used to measure run-time execution properties---for example, the frequency of method and statement execution. Such profiling could be applied to deployed software to gain performance insights about the behavior of many instances of the analyzed software. However, such data gathering raises privacy concerns: for example, it reveals whether (and how often) a software user accesses a particular software functionality. There is growing interest in adding privacy protections for many categories of data analyses, but such techniques have not been studied sufficiently for program event profiling. We propose the design of privacy-preserving event frequency profiling for deployed software. Each instance of the targeted software gathers its own event frequency profile and then randomizes it. The resulting noisy data has well-defined privacy properties, characterized via the powerful machinery of differential privacy. After gathering this data from many software instances, the profiling infrastructure computes estimates of population-wide frequencies while adjusting for the effects of the randomization. The approach employs static analysis to determine constraints that must hold in all valid run-time profiles, and uses quadratic programming to reduce the error of the estimates under these constraints. Our experiments study different choices for randomization and the resulting effects on the accuracy of frequency estimates. Our conclusion is that well-designed solutions can achieve both high accuracy and principled privacy-by-design for the fundamental problem of event frequency profiling.