> What you are suggesting, unless I am mistaken, is that new full nodes should have no way of knowing if an output is spent or even if it exists. Since large sections of the blockchain will potentially be skipped, the full node will not have complete knowledge of utxo's just for starters. So, this might not have been clear, but by "if we are given the liberty of modifying the protocol as we wish" I meant that I was discussing a protocol where these sorts of concerns are not an issue because we are not limited by the constraints of Bitcoin's current design. There have been plenty of proposals across the web for how to design a blockchain where what you're referring to is not an issue because of merkle commitments, etc., and some blockchains already do this (e.g. I believe Ethereum does this via parity). Cheers, Greg -- Please do not email me anything that you are not comfortable also sharing with the NSA. > On Feb 19, 2018, at 4:04 AM, Damian Williamson wrote: > > >1. Introducing state checkpoints into the chain itself could make it possible for full nodes to skip verification of large sections of historical data when booting up. > > What you are suggesting, unless I am mistaken, is that new full nodes should have no way of knowing if an output is spent or even if it exists. Since large sections of the blockchain will potentially be skipped, the full node will not have complete knowledge of utxo's just for starters. > > Regards, > Damian Williamson