Hi Greg,
>Here, you admit that the security of the sidechains allows miners to steal bitcoins, something they cannot do currently.
If I put my coins in an anyone can spend output, a miner will take them. They can do this today. I suggest you try it if you don't believe me :-). You have to be more specific with contract types instead of generically talking about 'all contracts ever'.
> Drivechain is an unmistakeable weakening of Bitcoin's security guarantees. This you have not denied.
I think this is an unfair characterization. You have to opt into using drivechains. Other outputs such as P2PKH/Multisig etc are unaffected by a drivechain output. As Pieter Wuille stated earlier in this thread (and Paul has stated all along), drivechain outputs have a different security model than other contracts. Namely they are controlled by miners. I think we can all agree this is unfortunate, but it is the current reality we live in. I look forward to the day we can solve the 'ownership' problem so we can have trustless interoperable blockchains, but that day is not today.
As a reminder, most users will not have to go through the drivechain withdrawal process. Most withdrawals will be done via atomic swaps.
>There is no reason to weaken Bitcoin's security in such a dramatic
fashion. Better options are being worked on, they just take time.
Everyone should re-read this email though, this is something that could happen. Paul's design makes it so that if this occurs it is *VERY* obvious. I guess we can argue if there is any difference between an obvious robbery vs a hidden robbery, but I think if we have to pick one or the other the choice is clear to me. Other designs (that I'm aware of) for sidechains had attack vectors that weren't so obvious.
-Chris