From: Johnson Lau <jl2012@xbt.hk>
Message-Id: <79668AE7-B05D-41F8-A6DF-EADC05143523@xbt.hk>
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Date: Wed, 25 Jan 2017 15:42:13 +0800
In-Reply-To: <CAAt2M1945e4jpy_eoZBJnyztVXjFVTJAjMc-u45gMf4ich8sEQ@mail.gmail.com>
To: Natanael <natanael.l@gmail.com>
References: <A182F080-F154-4F05-B2F1-21B90E469267@xbt.hk>
	<CAAt2M1_=8jDWuyO5_n8aXXDVYypvGQ2uL6zkJNn1ZnQOaXM6nQ@mail.gmail.com>
	<311FE02A-F3B5-4F88-B6C8-F0E78CC46903@xbt.hk>
	<CAAt2M1_cQTfaDyQkaixeFB5Ubi35fSOs9Ks74WZEehtFk__B3w@mail.gmail.com>
	<45F53199-C8AC-4DD3-B746-D56F9F01946B@xbt.hk>
	<CAAt2M1945e4jpy_eoZBJnyztVXjFVTJAjMc-u45gMf4ich8sEQ@mail.gmail.com>
Cc: bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Anti-transaction replay in a hardfork
Precedence: list


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> On 25 Jan 2017, at 15:29, Natanael <natanael.l@gmail.com> wrote:
>=20
>=20
> Den 25 jan. 2017 08:22 skrev "Johnson Lau" <jl2012@xbt.hk =
<mailto:jl2012@xbt.hk>>:
> Assuming Alice is paying Bob with an old style time-locked tx. Under =
your proposal, after the hardfork, Bob is still able to confirm the =
time-locked tx on both networks. To fulfil your new rules he just needs =
to send the outputs to himself again (with different tx format). But as =
Bob gets all the money on both forks, it is already a successful replay
>=20
> Why would Alice be sitting on an old-style signed transaction with =
UTXO:s none of which she controls (paying somebody else), with NO =
ability to substitute the transaction for one where she DOES control an =
output, leaving her unable to be the one spending the replay protecting =
child transaction?=20

If Alice still has full control, she is already protected by my =
proposal, which does not require any protecting child transaction.

But in many cases she may not have full control. Make it clearer, =
consider that=E2=80=99s actually a 2-of-2 multisig of Alice and Bob, and =
the time locked tx is sending to Bob. If the time locked tx is =
unprotected in the first place, Bob will get all the money from both =
forks anyway, as there is no reason for him to renegotiate with Alice.=

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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" =
class=3D""><br class=3D""><div><blockquote type=3D"cite" class=3D""><div =
class=3D"">On 25 Jan 2017, at 15:29, Natanael &lt;<a =
href=3D"mailto:natanael.l@gmail.com" =
class=3D"">natanael.l@gmail.com</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div dir=3D"auto" =
class=3D""><div data-smartmail=3D"gmail_signature" dir=3D"auto" =
class=3D""><br class=3D""></div><div class=3D"gmail_extra" =
dir=3D"auto"><div class=3D"gmail_quote">Den 25 jan. 2017 08:22 skrev =
"Johnson Lau" &lt;<a href=3D"mailto:jl2012@xbt.hk" =
class=3D"">jl2012@xbt.hk</a>&gt;:<br type=3D"attribution" =
class=3D""><blockquote class=3D"quote" style=3D"margin:0 0 0 =
.8ex;border-left:1px #ccc solid;padding-left:1ex"><div =
style=3D"word-wrap:break-word" class=3D""><div class=3D"">Assuming Alice =
is paying Bob with an old style time-locked tx. Under your proposal, =
after the hardfork, Bob is still able to confirm the time-locked tx on =
both networks. To fulfil your new rules he just needs to send the =
outputs to himself again (with different tx format). But as Bob gets all =
the money on both forks, it is already a successful =
replay</div></div></blockquote></div></div><div dir=3D"auto" =
class=3D""><br class=3D""></div><div dir=3D"auto" class=3D"">Why would =
Alice be sitting on an old-style signed transaction with UTXO:s none of =
which she controls (paying somebody else), with NO ability to substitute =
the transaction for one where she DOES control an output, leaving her =
unable to be the one spending the replay protecting child =
transaction?&nbsp;</div><div class=3D"gmail_extra" =
dir=3D"auto"></div></div>
</div></blockquote></div><br class=3D""><div class=3D""><div class=3D"">If=
 Alice still has full control, she is already protected by my proposal, =
which does not require any protecting child transaction.</div></div><div =
class=3D""><br class=3D""></div><div class=3D"">But in many cases she =
may not have full control. Make it clearer, consider that=E2=80=99s =
actually a 2-of-2 multisig of Alice and Bob, and the time locked tx is =
sending to Bob. If the time locked tx is unprotected in the first place, =
Bob will get all the money from both forks anyway, as there is no reason =
for him to renegotiate with Alice.</div></body></html>=

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