you do know that the main purpose of a blockchain is the preventing of double spends, do you?
So in DASH, the masternodes secure the blockchain (at least for IX-transactions). But I think I read somewhere that every transaction will be IX once evolution is out.
=> Masternodes secure the DASH blockchain.
I am perfectly aware, thank you.
I forgot to mention that Masternodes lock the transactions against double spend
instantly (hence IX), so you don't need to wait for block confirmation by the miners. Masternodes do not write to block though.
So to resume, Masternodes permit instant transactions while the miners secure the blockchain.
By the way, Masternodes also permit anonymity. It's a 2-tier network. The first of it's class. Soon to be a 3-tier.
It is perfectly possible (and maybe feasable) to let the masternodes write the blockchain.
Why not? If every transaction is IX, then the masternodes agree and are already responsible for securing the transactions...
So they can just write them to the blockchain as well: let the quorums just write a block.
plus side: DASH gives a bigger incentive to masternodes
PS: Ethereum is planning 1 second blocks (or even faster) so that will also be pretty instant.
They also work with a second tier: you need to have a security deposit to be able to do PoS validation.