...I wonder how you can have so much transactions per second? (the slide shows 500-1500) I read that bitcoin is limited to 7 transactions per second...
My thinking goes this far. Instant Transactions will have the input funds locked by a set of 10 masternodes chosen deterministically. There are 3,500 masternodes. Therefore 350 (3500/10) Instant Transactions (minus overhead) can be locked simultaneously. If this process can happen a couple of times every second, then 500-1500 is the answer.
If there are any devs watching that want to correct me, please do.
And the reason why it's secure against double spending is that those masternodes rule. You can't get past their locks. You can't get into a block if those funds are locked via another route. The block would be rejected by the network.