Title: Offline Assisted Group Key Exchange
|Affiliation:||Norwegian University of Science and Technology (NTNU)|
This talk will focus on the problem of forward secrecy in group key exchange (GKE), where most of the participants remain offline until they wish to compute the key. We give a a protocol for such a GKE that is well suited to a cloud storage environment: users are often offline, but have online access to the server which can assist in key exchange. To meet the scenario requirements we define and instantiate a new primitive, a blinded KEM, which we show can be used in a natural way as part of our generic protocol construction. Our protocol construction is provably secure in a well-known model for group key exchange, and is additionally efficient when implemented using our concrete instantiation. The talk will close with a discussion of the role of forward secrecy in group key exchange protocols, with a focus on practical application scenarios.
Joint work with Colin Boyd, Kristian Gjøsteen and Yao Jiang; to appear at ISC 2018; IACR ePrint 2018/114.