Offline Assisted Group Key Exchange
Journal article, Peer reviewed
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Original versionLecture Notes in Computer Science. 2018, 11060 LNCS 268-285. 10.1007/978-3-319-99136-8_15
We design a group key exchange protocol with forward secrecy where most of the participants remain offline until they wish to compute the key. This is well suited to a cloud storage environment where users are often offline, but have online access to the server which can assist in key exchange. 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 new protocol has a security proof based on a well-known model for group key exchange. Our protocol is efficient, requiring Diffie–Hellman with a handful of standard public key operations per user in our concrete instantiation.