Paper 2015/206

Efficient and Secure Delegation of Group Exponentiation to a Single Server

Bren Cavallo and Giovanni Di Crescenzo and Delaram Kahrobaei and Vladimir Shpilrain

Abstract

We consider the problem of delegating computation of group operations from a computationally weaker client holding an input and a description of a function, to a {\em single} computationally stronger server holding a description of the same function. Solutions need to satisfy natural correctness, security, privacy and efficiency requirements. We obtain delegated computation protocols for the following functions, defined for an {\em arbitrary} commutative group: \begin{enumerate} \item Group inverses, with security and privacy holding against any computationally unrestricted malicious server. \item Group exponentiation, with security and privacy holding against any computationally unrestricted ``partially honest" server. \item Group exponentiation, with security and privacy holding against any polynomial-time malicious server, under a pseudorandom generation assumption, and security holding with constant probability. \end{enumerate}