Evan Duffield revealed about his solution for 51% attack

He said: "The goal is to make a confirmationless wallet, where all transactions are protected by IX. 51% attacks become much less powerful in that case, they can't really touch IX. That would protect our millions of users we're currently shooting for (valid / non-illegal users btw), which leaves an attacker one option... to buy masternodes to attack Dash. We know how that will go.

We really do have an end-to-end solution to all problems within crypto now. I'm working on a 50+ page whitepaper that details the rest of the solution, I'm quite excited about it   

Here's another one for good measure. We have sub-quorums for super secure tasks, but we could implement full-quorum based actions the masternode network can take as a whole. For example, banning attacking pools from the network, people, countries, etc."