<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Jul 4, 2015 at 5:01 PM, Justus Ranvier <span dir="ltr"><<a href="mailto:justus@openbitcoinprivacyproject.org" target="_blank">justus@openbitcoinprivacyproject.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
</span>How do we know if a committed UTXO set is valid? If a majority of the<br>
hashing power is willing to extend an invalid branch, it's reasonable to<br>
assume they'd be willing to commit an invalid UTXO set as well.<br></blockquote><div><br></div><div>You can prove that it wasn't updated correctly.<br><br></div><div>For each transaction, the UTXO tree root before and after is committed.<br><br></div><div>You show the root before, and the root after and show that the after root is wrong. You also need to include some merkle paths to prove the transform.<br></div><div> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
</span>If items in the the proof tree are required to be sorted, then it's easy<br>
to proof that an item is missing.<br></blockquote><div><br></div><div>Yes, you can mostly get short proofs for each step, but you have to make sure your proofs are also provable.<br><br></div><div>It means going through everything that needs to be proved for a block to be valid.<br></div></div></div></div>