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From: Dan Libby <dan@osc.co.cr>
Message-ID: <5af10ca3-8b97-f227-c09f-901bbb6176c3@osc.co.cr>
Date: Thu, 13 Jul 2017 16:20:45 -0700
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Subject: Re: [bitcoin-dev] how to disable segwit in my build?
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Hampus, thanks for the explanation!

On 07/13/2017 03:50 PM, Hampus Sjöberg wrote:

> Yes.
> So you have two choices to be fully secure:
> 1. Validate using the new rules of the network (in other words, run a
> SegWit node)
> 2. Avoid any chain of transaction that contains a SegWit transaction

sounds good, though I'm unclear on how exactly to achieve (2) given that
any party I have ever transacted with (or otherwise knows an address of
mine) can send me coins at any time.  So it seems the only possible way
to be certain is to run a node that has never published an address to a
3rd party.  Is that accurate?

Another thing that could be done is to modify my own node so that it
actually rejects such tx, but then I have modified consensus rules
myself, thus defeating the goal of remaining with status-quo rules, and
anyway the rest of the network would accept the tx.  I guess the benefit
is that I could be certain of the remaining funds I have.

I suppose that it would be possible without modifying any rule to
construct a "certain balance" and an "uncertain balance".

I don't intend to do such modifications! just grasping for understanding.


> See
> https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#Backward_compatibility
> So the witness program is encoded in a new format that old nodes do not
> understand.
> This means that for old nodes, a number >0 will be put on the stack.
> When the script is done, it will be evaluated to true (because of >0)
> and be counted as a valid spend.
> 
> https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki also
> explains the new witness program more in detail (I left out some details
> in my explanation).

I read the relevant parts, thanks!