public void NewsDeriveKey(string chatRoomName)
{
ChatUser Bob = ChatingUsers.Find(x => x.ChatUserName == Context.User.Identity.Name);
ChatUser Alice = ChatingUsers.Find(x => x.ChatUserName != Context.User.Identity.Name && x.ChatRoomName == chatRoomName);
Clients.Group(chatRoomName).blockChat();
Alice.GenerateNewKey();
Bob.GenerateNewKey(Alice.PublicKey);
Alice.SetDeriveKey(Bob.PublicKey);
Alice.PreviousDeriveKey = null;
Bob.PreviousDeriveKey = null;
ChatingUsers[ChatingUsers.IndexOf(Alice)] = Alice;
ChatingUsers[ChatingUsers.IndexOf(Bob)] = Bob;
Clients.Group(chatRoomName).allowChat();
}