IACR News item: 05 February 2014
Craig Gentry, Shai Halevi, Mariana Raykova, Daniel Wichs
ePrint ReportThe starting point of this work is a subtle yet difficult-to-overcome issue with the Lu-Ostrovsky construction, that prevents a proof of security from going through. Specifically, the construction requires a complex \"circular\" use of Yao garbled circuits and PRFs. As our main result, we show how to remove this circularity and get a provably secure solution using *identity-based encryption* (IBE). We also abstract out, simplify and generalize the main ideas behind the Lu-Ostrovsky construction, making them easier to understand and analyze.
In a companion work to ours (Part II), Lu and Ostrovsky show an alternative approach to solving the circularity problem. Their approach relies only on the existence of one-way functions, at the price of higher overhead. Specifically, our construction has overhead $\\poly(k)\\polylog(n)$ (with $k$ the security parameter and $n$ the data size), while the Lu-Ostrovsky approach can achieve overhead $\\poly(k)n^\\eps$ for any constant $\\eps>0$. It remains as an open problem to achieve an overhead of $\\poly(k)\\polylog(n)$ assuming only the existence of one-way functions.
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