The Taub Faculty of Computer Science Events and Talks

Our research focuses on new techniques for homomorphic secret sharing (HSS) which is a promising new cryptographic tool for privacy-preserving computations. HSS can be seen as a relaxation of fully homomorphic encryption (FHE), the latter being an encryption with the capability to perform calculations on encrypted data without decrypting first.

FHE is a well-studied topic in cryptography that has recently attracted a lot of research both in academia and in the industry. However, the efficiency of state-of-the-art solutions leaves much to be desired. HSS relaxes the notion of FHE by allowing the data to be secret-shared among two or more non-colluding servers, as opposed to being encrypted on a single server.

HSS has several advantages over FHE. On the theory side, non-trivial HSS schemes exist based on symmetric (“private key”) cryptography or even with information-theoretic (“perfect”) security. On the practical side, these low-end HSS solutions are orders of magnitude faster than the single-server FHE solutions and have better concrete communication costs. Our research explores new approaches to constructing efficient HSS schemes by improving the generality, communication complexity, and computational cost of existing techniques. As a special case, this has relevance to multi-server private information retrieval (PIR), a form of HSS for table lookup which is a powerful building block for privacy-preserving database searches.