Functional encryption (FE) is an encryption paradigm that allows for the delegation of fine-grained access control over encrypted data using so-called functional keys. The standard security notion of FE protects against a potentially malicious decryptor; it ensures that an adversary does not learn more about the encrypted data than what is leaked from the functional keys. In this talk, we present the notion of consistency; a new security definition for FE that protects against a potentially malicious encryptor and/or setup generator. Furthermore, we analyze the implications of standard single-input FE in the multi-client setting. We show that it is possible to construct multi-client FE for separable functions from a general-purpose standard FE scheme. Additionally, we present a compiler based on multi-key fully homomorphic encryption that reduces the communication complexity of existing multiparty computation (MPC) protocols. MPC can be seen as an interactive version of FE where several parties jointly evaluate a function over their inputs. Applying our compiler to the recent constructions of round-optimal MPC protocols, we obtain the first class of round-optimal and communication-efficient MPC protocols.
Hendrik Waldner is a Ph.D. student at the University of Edinburgh supervised by Prof. Aggelos Kiayias. His research interests are in cryptography and more broadly theoretical computer science. During his Ph.D. studies he has mainly worked in the area of functional encryption, where he constructed new multi-client schemes and introduced new security definitions. More recently, he has been exploring multiparty computation, resulting in the first class of round and communication optimal multiparty computation protocols. Previous to his Ph.D. studies, he obtained a degree in Mathematics from the Ruhr-University Bochum.
Part of the Illinois Computer Science Speakers Series. Faculty Host: Dakshita Khurana