Quote from: YourFriendlyNig on February 21, 2014, 08:19:22 PM

I don't know much about programming, but what does it mean by the fact that all the script signatures are redacted?

I'm not quite sure what you're asking for, so sorry if I my answer is not what you expected.

The ntxid is calculated the same way that the txid is calculated, but by removing all scripts. Why? The idea is that the scripts themselves are not signed (and cannot easily be), whereas other part of the transactions are signed. Now an attacker may make a subtle modification to the script; and since the scripts are not signed, even if the attacter does not have the private key, the transaction remains valid.

There is now two similar but different transactions. They both have the same effect: "transferring n bitcoins form X to Y" (this data is signed). But because they have the same effect, only one of them can confirm. We say that that one of them is mutated (but to a miner, who don't know the sender, he cannot tell which is which, both being equally valid). Their txid is different, because the transactions are slightly different.

If the "mutated" one confirms, it may confuse the sender if the sender only checks if a given txid is confirmed.

The ntxid is a solution to that: By blanking the scripts, the ntxid is the same for ALL transactions that have the same effect. Since this data is controlled/signed by the sender, he can now be sure that if he checks for confirmation of a given ntxid, he will know, even if it is a mutated version that confirms.

(The original txid remains useful because the nodes need a way to discern the different-but-equally-valid mutated versions one from the other.)