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From: Matias Alejo Garcia <matias@bitpay.com>
Date: Mon, 5 Oct 2015 03:57:16 -0300
Message-ID: <CA+vKqYeBDHEGRgCsuAp3wQKb9idH085e5K3uNdeRLFvc9MTpdQ@mail.gmail.com>
To: Thomas Kerin <thomas.kerin@gmail.com>
Content-Type: multipart/alternative; boundary=001a1140c1c43fd32c0521560717
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] [Bitcoin-development] New BIP32 structure for
 P2SH multisig wallets [BIP-45]
Precedence: list

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Hi,

Sorry the late response. Going back to the original message:


> > On 03/10/15 13:42, Jean-Pierre Rupp via bitcoin-dev wrote:
> >> I have been reviewing BIP-45 today.  There is a privacy problem with i=
t
> >> that should at least be mentioned in the document.
> >>
> >> When using the same extended public key for all multisig activity, and
> >> dealing with different cosigners in separate multisig accounts, reuse =
of
> >> the same set of public keys means that all cosigners from all accounts
> >> will be able to monitor multisig activity from every other cosigner, i=
n
> >> every other account.
>

I am not completely sure what you mean by 'account' and 'mutisig activity'.
You seem to imply
that the same set of extended public keys will be used in more that one
wallet, which it is
not required (and certainly not recommended) by BIP45.

According to BIP45, a singing party, in order to generate a wallet address,
needs the extended public keys of all the other parties, so each party will
be able to see the transaction history of the wallet they are sharing, but
if the party has other wallets with other copayers the xpub should be
completely different.

mat=C3=ADas



--=20
BitPay.com

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><div=
><br></div><div>Hi,</div><div><br></div><div>Sorry the late response. Going=
 back to the original message:</div><div>=C2=A0</div><blockquote class=3D"g=
mail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-l=
eft:1ex">&gt; On 03/10/15 13:42, Jean-Pierre Rupp via bitcoin-dev wrote:<br=
>
&gt;&gt; I have been reviewing BIP-45 today.=C2=A0 There is a privacy probl=
em with it<br>
&gt;&gt; that should at least be mentioned in the document.<br>
&gt;&gt;<br>
&gt;&gt; When using the same extended public key for all multisig activity,=
 and<br>
&gt;&gt; dealing with different cosigners in separate multisig accounts, re=
use of<br>
&gt;&gt; the same set of public keys means that all cosigners from all acco=
unts<br>
&gt;&gt; will be able to monitor multisig activity from every other cosigne=
r, in<br>
&gt;&gt; every other account.<br></blockquote><div><br></div><div>I am not =
completely sure what you mean by &#39;account&#39; and &#39;mutisig activit=
y&#39;. You seem to imply</div><div>that the same set of extended public ke=
ys will be used in more that one wallet, which it is=C2=A0</div><div>not re=
quired (and certainly not recommended) by BIP45.</div><div><br></div><div>A=
ccording to BIP45, a singing party, in order to generate a wallet address, =
needs the extended public keys of all the other parties, so each party will=
 be able to see the transaction history of the wallet they are sharing, but=
 if the party has other wallets with other copayers the xpub should be comp=
letely different.</div><div><br></div><div>mat=C3=ADas</div><div><br></div>=
<div><br></div></div><div><br></div>-- <br><div class=3D"gmail_signature"><=
div dir=3D"ltr"><div>BitPay.com</div></div></div>
</div></div>

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