On Sat, May 16, 2015 at 4:58 AM, Stephen <stephencalebmorse@gmail.com> wrote:

We should make sure to consider how BIP34 affects normalized transaction ids, since the height of the block is included in the scriptSig ensuring that the txid will be different. We wouldn't want to enable replay attacks in the form of spending coinbase outputs in the same way they were spent from a previous block.

So maybe normalized txids should strip the scriptSigs of all transactions except for coinbase transactions? This seems to make sense, since coinbase transactions are inherently not malleable anyway.

That is a good point. Since the point is the change is to use good practice right back until the genesis block, maybe the scriptSig for coinbases could be replaced by the height expressed as a varint. That means that all coinbases get a unique normalized txid. The coinbases with duplicate txids still wouldn't be spendable though.