Secure function evaluation (SFE) on mobile devices, such as smartphones, creates compelling new applications such as privacy-preserving bartering. Generating custom garbled circuits on smartphones, however, is infeasible for all but the most trivial problems due to the high memory overhead incurred. In this paper, we develop a new methodology of generating garbled circuits that is memory-efficient. Using the standard SFDL language for describing secure functions as input, we design a new pseudo-assembly language (PAL) and a template-driven compiler that generates circuits which can be evaluated with Fairplay. We deploy this compiler for Android devices and demonstrate that a large new set of circuits can now be generated on smartphones, with memory overhead for the set intersection problem reduced by 95.6% for the 2-set case. We develop a password vault application to show how runtime generation of circuits can be used in practice. We also show that our circuit generation techniques can be used in conjunction with other SFE optimizations. These results demonstrate the feasibility of generating garbled circuits on mobile devices while maintaining high-level function specification.
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