MIME-Version: 1.0
In-Reply-To: <etPan.54d0b945.46e87ccd.7f23@Williams-MBP>
References: <etPan.54d0b945.46e87ccd.7f23@Williams-MBP>
Date: Tue, 3 Feb 2015 14:25:19 -0500
Message-ID: <CAFVoEQQHVcY0Ad-4c2wnH+WF_7M-o5SNwVr-nce_9bQ794cwDQ@mail.gmail.com>
From: Adam Weiss <adam@signal11.com>
To: Will <will.madden@novauri.com>
Content-Type: multipart/alternative; boundary=089e0149d0940f2d89050e3408d5
Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] Subject: Re: Proposal to address Bitcoin
	malware
Precedence: list

--089e0149d0940f2d89050e3408d5
Content-Type: text/plain; charset=UTF-8

>
>
> Using a desktop website and mobile device for 2/3 multisig in lieu of a
> hardware device (trezor) and desktop website (mytrezor) works, but the key
> is that the device used to input the two signatures cannot be in the same
> band.  What you are protecting against are MITM attacks.  The issue is that
> if a single device or network is compromised by malware, or if a party is
> connecting to a counterparty through a channel with compromised security,
> inputing 2 signatures through the same device/band defeats the purpose of
> 2/3 multisig.
>

Maybe I'm not following the conversation very well, but if you have a small
hardware device that first displays a signed payment request (BIP70) and
then only will sign what is displayed, how can a MITM attacker do anything
other than deny service?  They'd have to get malware onto the signing
device, which is the vector that a simplified signing device is
specifically designed to mitigate.

TREZOR like devices with BIP70 support and third party cosigning services
are a solution I really like the sound of.  I suppose though that adding
BIP70 request signature validation and adding certificate revocation
support starts to balloon the scope of what is supposed to be a very simple
device though.

Regardless, I think a standard for passing partially signed transactions
around might make sense (maybe a future extension to BIP70), with attention
to both PC <-> small hardware devices and pushing stuff around on the
Internet.  It would be great if users had a choice of hardware signing
devices, local software and third-party cosigning services that would all
interoperate out of the box to enable easy multisig security, which in the
BTC world subsumes the goals of 2FA.

--adam

--089e0149d0940f2d89050e3408d5
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #c=
cc solid;padding-left:1ex"><div style=3D"word-wrap:break-word"><div style=
=3D"font-family:Helvetica,Arial;font-size:13px;color:rgba(0,0,0,1.0);margin=
:0px;line-height:auto"><span style=3D"font-family:&#39;helvetica Neue&#39;,=
helvetica;line-height:19.5px"><br></span></div><div style=3D"margin:0px"><f=
ont face=3D"helvetica Neue, helvetica"><span style=3D"line-height:19.5px">U=
sing a desktop website and mobile device for 2/3 multisig in lieu of a hard=
ware device (trezor) and desktop website (mytrezor) works, but the key is t=
hat the device used to input the two signatures=C2=A0cannot be in the same =
band.=C2=A0 What you are protecting against are MITM attacks.=C2=A0 The iss=
ue is that if a single=C2=A0device or network is compromised by malware, or=
 if a party is connecting to a counterparty through a channel with compromi=
sed security, inputing 2 signatures through the=C2=A0same device/band defea=
ts=C2=A0the purpose of 2/3 multisig. =C2=A0</span></font></div></div></bloc=
kquote><div><br></div><div>Maybe I&#39;m not following the conversation ver=
y well, but if you have a small hardware device that first displays a signe=
d payment request (BIP70) and then only will sign what is displayed, how ca=
n a MITM attacker do anything other than deny service?=C2=A0 They&#39;d hav=
e to get malware onto the signing device, which is the vector that a simpli=
fied signing device is specifically designed to mitigate.</div><div><br></d=
iv><div>TREZOR like devices with BIP70 support and third party cosigning se=
rvices are a solution I really like the sound of.=C2=A0 I suppose though th=
at adding BIP70 request signature validation and adding certificate revocat=
ion support starts to balloon the scope of what is supposed to be a very si=
mple device though.</div><div><br></div><div>Regardless, I think a standard=
 for passing partially signed transactions around might make sense (maybe a=
 future extension to BIP70), with attention to both PC &lt;-&gt; small hard=
ware devices and pushing stuff around on the Internet.=C2=A0 It would be gr=
eat if users had a choice of hardware signing devices, local software and t=
hird-party cosigning services that would all interoperate out of the box to=
 enable easy multisig security, which in the BTC world subsumes the goals o=
f 2FA.</div><div><br></div><div>--adam<br></div><div><br></div></div></div>=
</div>

--089e0149d0940f2d89050e3408d5--