Lockable Obfuscation
Venkata Koppula
Abstract:
This talk, based on a recent work (http://eprint.iacr.org/2017/274) will be about the notion of lockable obfuscation. We present an LWE based construction for lockable obfuscation and show some applications.
In a lockable obfuscation scheme there exists an obfuscation algorithm Obf that takes as input a security parameter \lambda, a program P, a message msg and ``lock value'' \alpha and outputs an obfuscated program P'. One can evaluate the obfuscated program P' on any input x where the output of evaluation is the message msg if P(x) = \alpha and otherwise receives a rejecting symbol \bot.
We proceed to provide a construction of lockable obfuscation and prove it secure under the Learning with Errors (LWE) assumption. We follow this by describing multiple applications of lockable obfuscation. First, we show how to transform any attribute-based encryption (ABE) scheme into one in which the attributes used to encrypt the message are hidden from any user that is not authorized to decrypt the message. The only previous construction due to Gorbunov, Vaikuntanathan and Wee is based off of a specific ABE scheme of Boneh et al. By enabling the transformation of any ABE scheme we can inherent different forms and features of the underlying scheme such as: multi-authority, adaptive security from polynomial hardness, regular language policies, etc. We also show other applications such as circular security separations and random oracle uninstantiability results.
Joint work with Rishab Goyal and Brent Waters