Den 22 feb 2015 13:36 skrev "Peter Todd" <pete@petertodd.org>:
> Implementing it as a general purpose scripting language improvement has
> a lot of advantages, not least of which is that you no longer need to
> rely entirely on inherently unreliable P2P networking: Promise to never
> create two signatures for a specific BIP32 root pubkey and make
> violating that promise destroy and/or reallocate a fidelity bond whose
> value is locked until some time into the future. Since the fidelity bond
> is a separate pool of funds, detection of the double-spend can happen
> later.

Somebody sent me a zero-confirmation transaction, or one that got orphaned after one block. I created a transaction spending that UTXO, and another.

So at that point I have UTXO_orphaned based on the sender's UTXO_origin and my UTXO_old (because I've had it unspent for a long time), both in one transaction, creating UTXO_new.

Now he doublespend UTXO_origin to create a UTXO_doublespend (which conflicts with UTXO_orphaned). He conspires with a miner to get it into a block.

Now what? Can my UTXO_old effectively be tainted forever because UTXO_new got invalidated together with UTXO_orphaned? Will that transaction be a valid proof of doublespend against a new UTXO_replacement I created?

Or otherwise, if only transactions where all UTXO's are currently valid works as doublespend proofs, aren't you still just left without protection against any one miner that conspires with doublespend attempting thieves?

In other words, you are unprotected and potentially at greater risk if you create a transaction depending on another zero-confirmation transaction.