Indistinguishability Obfuscation with Constant Size Overhead

Present constructions of indistinguishability obfuscation (iO) create obfuscated programs where the size of the obfuscated program is at least a factor of a security parameter larger than the size of the original program. In this work, we construct the first iO scheme that achieves only a constant multiplicative overhead (in fact, the constant is 2) in the size of the program. The security of our construction requires the existence of sub-exponentially secure iO for circuits (that has any polynomial multiplicative overhead in the circuit size) and one-way functions.