  A common tool used by security professionals for reverse-engineering binaries
found in the wild is the decompiler. A decompiler attempts to reverse
compilation, transforming a binary to a higher-level language such as C.
High-level languages ease reasoning about programs by providing useful
abstractions such as loops, typed variables, and comments, but these
abstractions are lost during compilation. Decompilers are able to
deterministically reconstruct structural properties of code, but comments,
variable names, and custom variable types are technically impossible to
recover.
  In this paper we present DIRTY (DecompIled variable ReTYper), a novel
technique for improving the quality of decompiler output that automatically
generates meaningful variable names and types. Empirical evaluation on a novel
dataset of C code mined from GitHub shows that DIRTY outperforms prior work
approaches by a sizable margin, recovering the original names written by
developers 66.4% of the time and the original types 75.8% of the time.
