date:Jan.31 2020
Title : Key Re-usable Dynamic Group Key Exchange from Lattice against Neighbor Attacks

Recently, several key reuse attacks against Ding Key Exchange, NewHope and other lattice-based key exchange schemes
using Peikert's key reconciliation mechanism were suggested. But all known key reuse attacks are designed for two-party setting instead of group key exchange.
On the other hand, all previous known lattice-based group key exchanges are designed for static setting.

In this talk, we present the first key reuse attack called {one, two}- neighbour attack against lattice-based group key exchanges, namely Ding et al.'s group key exchange
scheme in 2012 and Apon et al.'s group key exchange scheme (PQCrypto 2019).
Then, using the existing pasteurization technique, we describe the first key-reusable dynamic group key exchange without trusted authority against neighbor attacks.
Our dynamic group key exchange protocol can be considered to be a kind of the tweak of Dutta-Barua protocol in RLWE setting.