Secure Physical Computation Using Disposable Circuits

In a

secure physical computation

, a set of parties each have physical inputs and jointly compute a function of their inputs in a way that reveals no information to any party except for the output of the function. Recent work in CRYPTO’14 presented examples of physical

zero-knowledge

proofs of physical properties, a special case of secure physical two-party computation in which one party has a physical input and the second party verifies a boolean function of that input. While the work suggested a general framework for modeling and analyzing physical zero-knowledge protocols, it did not provide a general theory of how to prove any physical property with zero-knowledge. This paper takes an orthogonal approach using

disposable circuits

(DC)—cheap hardware tokens that can be completely destroyed after a computation—an extension of the familiar tamper-proof token model. In the DC model, we demonstrate that two parties can compute any function of their physical inputs in a way that leaks at most 1 bit of additional information to either party. Moreover, our result generalizes to any multi-party physical computation. Formally, our protocols achieve unconditional UC-security with input-dependent abort.