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Date: Fri, 4 Apr 2014 15:54:52 +0200
Message-ID: <CANEZrP2Z5x0_kOQ=8-BMzbmi9=D=ou=s3dgEksMA5F84BHSt9A@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: =?UTF-8?Q?Eric_Larchev=C3=AAque?= <elarch@gmail.com>
Content-Type: multipart/alternative; boundary=047d7b6769e8b04e0d04f637dc91
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Draft BIP for seamless website
 authentication using Bitcoin address
Precedence: list

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>
> What if I do a shared spend/CoinJoin type tx? Now anyone who took part in
> the shared tx with me can get into my hotel room too?
>

Oh, if these seem too abstract, also consider bitbanks. In an ideal world
nobody would outsource running of their Bitcoin wallet, but sadly people
do, so then they don't control the private keys at all.

The goal of writing a BIP seems to be to get lots of different wallet
authors to write lots of code for you - but I *am* a wallet author, and I
don't think that's the right way to get traction with a new scheme. For
instance the TREZOR guys would have to support your new protocol otherwise
if I paid my hotel bill with my TREZOR I couldn't open the door when I got
there! But they probably have better things to be doing right now.

The key difference between just generating a client certificate and using a
Bitcoin address is that the client certificate is something that is used
*specifically* for identification. It leaves no trace in the block chain,
so no weird privacy issues, it doesn't matter how you manage your wallet,
and you don't have to persuade lots of people to support your idea because
it was already done >10 years ago and basically every browser/web server
supports it.

Some reasons client certs aren't more widely used boil down to:

   1. People like passwords. In particular they like forgetting them and
   then having friendly people assist them to get it back. Client certs can
   support this use case, but only if apps are checking the identity in them
   and not the key.
   2. The UI for managing client certs in browsers is pretty horrible.
   There's little incentive to improve it because of (1).
   3. Cross-device sync doesn't work very well. Apple are starting to
   tackle this with their iCloud Keychain Sync service but then of course,
   Apple has all your keys and you may well just sign in to things with your
   Apple account (if it were to be supported). Cross-device sync where the
   server *doesn't* get your keys is supported by Chrome for passwords, but
   not client certs, because (1)

None of the above issues have any obvious fix lurking within Bitcoin.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;paddi=
ng-left:1ex">
<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><div=
>What if I do a shared spend/CoinJoin type tx? Now anyone who took part in =
the shared tx with me can get into my hotel room too?</div></div></div></di=
v>
</blockquote><div><br></div><div>Oh, if these seem too abstract, also consi=
der bitbanks. In an ideal world nobody would outsource running of their Bit=
coin wallet, but sadly people do, so then they don&#39;t control the privat=
e keys at all.</div>
<div><br></div><div>The goal of writing a BIP seems to be to get lots of di=
fferent wallet authors to write lots of code for you - but I <i>am</i>=C2=
=A0a wallet author, and I don&#39;t think that&#39;s the right way to get t=
raction with a new scheme. For instance the TREZOR guys would have to suppo=
rt your new protocol otherwise if I paid my hotel bill with my TREZOR I cou=
ldn&#39;t open the door when I got there! But they probably have better thi=
ngs to be doing right now.</div>
<div><br></div><div>The key difference between just generating a client cer=
tificate and using a Bitcoin address is that the client certificate is some=
thing that is used <i>specifically</i>=C2=A0for identification. It leaves n=
o trace in the block chain, so no weird privacy issues, it doesn&#39;t matt=
er how you manage your wallet, and you don&#39;t have to persuade lots of p=
eople to support your idea because it was already done &gt;10 years ago and=
 basically every browser/web server supports it.</div>
<div><br></div><div>Some reasons client certs aren&#39;t more widely used b=
oil down to:</div><div><ol><li>People like passwords. In particular they li=
ke forgetting them and then having friendly people assist them to get it ba=
ck. Client certs can support this use case, but only if apps are checking t=
he identity in them and not the key.</li>
<li>The UI for managing client certs in browsers is pretty horrible. There&=
#39;s little incentive to improve it because of (1).<br></li><li>Cross-devi=
ce sync doesn&#39;t work very well. Apple are starting to tackle this with =
their iCloud Keychain Sync service but then of course, Apple has all your k=
eys and you may well just sign in to things with your Apple account (if it =
were to be supported). Cross-device sync where the server <i>doesn&#39;t</i=
>=C2=A0get your keys is supported by Chrome for passwords, but not client c=
erts, because (1)</li>
</ol><div>None of the above issues have any obvious fix lurking within Bitc=
oin.</div></div></div></div></div>

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