[Bitcoin-development] Duplicate transactions vulnerability

[Gregory Maxwell]

On Thu, Mar 1, 2012 at 8:09 AM, Ben Reeves <support at pi.uk.com> wrote:
> One more thing to add. The implementation in the reference patch fixes
> the blockchain forking issue however by still allowing spent coinbases
> to be disconnected patched clients are still vulnerable to blockchain
> corruption. While not an immediate issue it would mean
> LoadBlockIndex() would error on restart and could cause problems for
> new clients during the initial blockchain download.

I am not following you here, can you explain what you're thinking?

> Is there a reason not to disallow duplicate coinbases entirely?

Because this would make it impossible for nodes to prune the vaules.
They'd all forever have to keep a set of all the coinbase hashes in
order to perform the test. The height-in-coinbase BIP will make
duplicates effectively impossible to create, which is a much more
clean behavior.