/* Triple Diffie-Hellman authentication */ Note added about order of users
By using TDH secret both in p2p key as well as in key confirmation step, (n+1)sec both implicitly and explicitly authenticate the peers.
In Algorithm 1, TDH and the original group key exchange from [ACMP10] has been combined to provide a deniable authenticated group key exchange. Here, we single out TDH Algorithm 1.1 for better presentation of the protocol for the reader.
'''Algorithm 1.1''' Triple Diffie-Hellman between <math>U_i</math> and <math>U_j</math> assuming i < j