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From: James MacWhyte <macwhyte@gmail.com>
Date: Wed, 10 Aug 2016 04:31:11 +0000
Message-ID: <CAH+Axy4J5vsi61eX_w1V=e2DdkttTBsbUcwXdqrgchJ6GXdaow@mail.gmail.com>
To: tony.991@gmail.com
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Hiding entire content of on-chain transactions
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Signed by the key pair that was referenced in the output of the on-chain
transaction? (Bob in my example, actually) Doesn't that mean it's easy to
follow who is paying whom, you just can't see how much is going to reach
recipient?

On Tue, Aug 9, 2016, 04:40 Tony Churyumoff <tony991@gmail.com> wrote:

> This troll is harmless.  A duplicate spend proof should also be signed
> by the same user (Alice, in your example) to be considered a double
> spend.
>
> 2016-08-09 3:18 GMT+03:00 James MacWhyte <macwhyte@gmail.com>:
> > One more thought about why verification by miners may be needed.
> >
> > Let's say Alice sends Bob a transaction, generating output C.
> >
> > A troll, named Timothy, broadcasts a transaction with a random hash,
> > referencing C's output as its spend proof. The miners can't tell if it's
> > valid or not, and so they include the transaction in a block. Now Bob's
> > money is useless, because everyone can see the spend proof referenced and
> > thinks it has already been spent, even though the transaction that
> claims it
> > isn't valid.
> >
> > Did I miss something that protects against this?
> >
>

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<div dir=3D"ltr">Signed by the key pair that was referenced in the output o=
f the on-chain transaction? (Bob in my example, actually) Doesn&#39;t that =
mean it&#39;s easy to follow who is paying whom, you just can&#39;t see how=
 much is going to reach recipient?</div><span>
</span><br><div class=3D"gmail_quote"><div dir=3D"ltr">On Tue, Aug 9, 2016,=
 04:40 Tony Churyumoff &lt;<a href=3D"mailto:tony991@gmail.com" target=3D"_=
blank">tony991@gmail.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail=
_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:=
1ex">This troll is harmless.=C2=A0 A duplicate spend proof should also be s=
igned<br>
by the same user (Alice, in your example) to be considered a double<br>
spend.<br>
<br>
2016-08-09 3:18 GMT+03:00 James MacWhyte &lt;<a href=3D"mailto:macwhyte@gma=
il.com" target=3D"_blank">macwhyte@gmail.com</a>&gt;:<br>
&gt; One more thought about why verification by miners may be needed.<br>
&gt;<br>
&gt; Let&#39;s say Alice sends Bob a transaction, generating output C.<br>
&gt;<br>
&gt; A troll, named Timothy, broadcasts a transaction with a random hash,<b=
r>
&gt; referencing C&#39;s output as its spend proof. The miners can&#39;t te=
ll if it&#39;s<br>
&gt; valid or not, and so they include the transaction in a block. Now Bob&=
#39;s<br>
&gt; money is useless, because everyone can see the spend proof referenced =
and<br>
&gt; thinks it has already been spent, even though the transaction that cla=
ims it<br>
&gt; isn&#39;t valid.<br>
&gt;<br>
&gt; Did I miss something that protects against this?<br>
&gt;<br>
</blockquote></div>

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