Circuit-Free General-Purpose Multi-Party Computation via Co-Utile Unlinkable Outsourcing

Identifier:  imarina:9243283

Handle: https://hdl.handle.net/20.500.11797/imarina9243283

Authors:  Domingo-Ferrer, Josep; Manjon, Jesus

Abstract:
Multiparty computation (MPC) consists in several parties engaging in joint computation in such a way that each partys input and output remain private to that party. MPC protocols for specific computations have existed since the 1980s, but only recently general-purpose compilers have been developed to allow MPC on arbitrary functions. Yet, using todays MPC compilers requires substantial programming effort and skill, inter alia because most compilers translate the code of the computation into a Boolean or arithmetic circuit. The circuit representation requires unrolling loops and recursive calls, which forces programmers to define loop bounds and hardly use recursion. We present an approach allowing MPC on an arbitrary computation expressed as ordinary code with all functionalities that does not need to be translated into a circuit. Our notion of input and output privacy is predicated on unlinkability. Our method leverages co-utile computation outsourcing using anonymous channels via decentralized reputation, makes a minimalistic use of cryptography and does not require participants to be honest-but-curious: it works as long as participants are rational (self-interested). We present example applications, including e-voting. Our empirical work shows that reputation captures well the behavior of peers and ensures that parties with high reputation obtain correct results.