Abstract
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.
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Notes
- 1.
This practice is confusingly often called zero knowledge in commercial circles.
- 2.
We abuse nomenclature throughout the rest of the paper and use ‘encapsulation’ to refer to a key encapsulation that is yet to be blinded.
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Boyd, C., Davies, G.T., Gjøsteen, K., Jiang, Y. (2018). Offline Assisted Group Key Exchange. In: Chen, L., Manulis, M., Schneider, S. (eds) Information Security. ISC 2018. Lecture Notes in Computer Science(), vol 11060. Springer, Cham. https://doi.org/10.1007/978-3-319-99136-8_15
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