Paper 2013/774

Multi-Input Functional Encryption

S. Dov Gordon, Jonathan Katz, Feng-Hao Liu, Elaine Shi, and Hong-Sheng Zhou

Abstract

\emph{Functional encryption} (FE) is a powerful primitive enabling fine-grained access to encrypted data. In an FE scheme, secret keys (``tokens'') correspond to functions; a user in possession of a ciphertext $\text{ct}=\text{enc}(x)$ and a token $\text{tkf}$ for the function~$f$ can compute $f(x)$ but learn nothing else about~$x$. An active area of research over the past few years has focused on the development of ever more expressive FE schemes. In this work we introduce the notion of \emph{multi-input} functional encryption. Here, informally, a user in possession of a token $$ for an $$-ary function $$ and \emph{multiple} ciphertexts $$, \ldots, $$ can compute $$ but nothing else about the~$$. Besides introducing the notion, we explore the feasibility of multi-input FE in the public-key and symmetric-key settings, with respect to both indistinguishability-based and simulation-based definitions of security.