Peter Todd [ARCHIVE] on Nostr: 📅 Original date posted:2019-10-05 📝 Original message:On Fri, Oct 04, 2019 at ...

📅 Original date posted:2019-10-05
📝 Original message:On Fri, Oct 04, 2019 at 11:40:53AM -0700, Jeremy wrote:
> Interesting point.
>
> The script is under your control, so you should be able to ensure that you
> are always using a correctly constructed midstate, e.g., something like:
>
> scriptPubKey: <-1> OP_SHA256STREAM DEPTH OP_SHA256STREAM <-2>
> OP_SHA256STREAM
> <hash> OP_EQUALVERIFY
>
> would hash all the elements on the stack and compare to a known hash.
> How is that sort of thing weak to midstateattacks?

Obviously with care you can get the computation right. But at that point what's
the actual advantage over OP_CAT?

We're limited by the size of the script anyway; if the OP_CAT output size limit
is comparable to that for almost anything you could use SHA256STREAM on you
could just as easily use OP_CAT, followed by a single OP_SHA256.

--
https://petertodd.org 'peter'[:-1]@petertodd.org
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