Obfuscation by partial evaluation of distorted interpreters

  • Authors:

  • Roberto Giacobazzi;Neil D. Jones;Isabella Mastroeni

  • Affiliations:

  • University of Verona, Verona, Italy;University of Copenhagen, Copenhagen, Denmark;University of Verona, Verona, Italy

  • Venue:
  • PEPM '12 Proceedings of the ACM SIGPLAN 2012 workshop on Partial evaluation and program manipulation
  • Year:
  • 2012

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Abstract

How to construct a general program obfuscator? We present a novel approach to automatically generating obfuscated code P2 from any program P whose source code is given. Start with a (program-executing) interpreter interp for the language in which P is written. Then "distort" interp so it is still correct, but its specialization P2 w.r.t. P is transformed code that is equivalent to the original program, but harder to understand or analyze. Potency of the obfuscator is proved with respect to a general model of the attacker, modeled as an approximate (abstract) interpreter. A systematic approach to distortion is to make program P obscure by transforming it to P2 on which (abstract) interpretation is incomplete. Interpreter distortion can be done by making residual in the specialization process sufficiently many interpreter operations to defeat an attacker in extracting sensible information from transformed code. Our method is applied to: code flattening, data-type obfuscation, and opaque predicate insertion. The technique is language independent and can be exploited for designing obfuscating compilers.