Garbled circuits via structured encryption

The garbled circuit technique transforms a circuit in such a way that it can be evaluated on encrypted inputs. Garbled circuits were originally introduced by Yao (FOCS ’86) for the purpose of secure
two-party computation but have since found many applications.

In this work, we consider the problem of designing special-purpose garbled circuits, which are garbled circuits that handle only a specific class of functionalities. Special-purpose constructions are usually smaller than general-purpose ones and lead to more efficient two-party protocols.

We propose a design framework for constructing special-purpose garbled circuits based on structured encryption schemes, which are encryption schemes that encrypt data structures in such a way that they can be queried through the use of a token. Using our framework, we show how to design more efficient garbled circuits for several graph-based functionalities (with applications to online social network analysis), Boolean circuits, deterministic finite automata, and branching programs.