summaryrefslogtreecommitdiff
path: root/6b/a49574b7feb9f9fed93d34a5e5c7179d0c2222
blob: c23db5c81d1202d6ad28f5b5c0ebe80529ae2e16 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193]
	helo=mx.sourceforge.net)
	by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76)
	(envelope-from <eric@voskuil.org>) id 1YJWgZ-0007Mw-3L
	for bitcoin-development@lists.sourceforge.net;
	Fri, 06 Feb 2015 00:22:15 +0000
X-ACL-Warn: 
Received: from mail-pa0-f52.google.com ([209.85.220.52])
	by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128)
	(Exim 4.76) id 1YJWgX-0003ac-Pn
	for bitcoin-development@lists.sourceforge.net;
	Fri, 06 Feb 2015 00:22:15 +0000
Received: by mail-pa0-f52.google.com with SMTP id kq14so5782172pab.11
	for <bitcoin-development@lists.sourceforge.net>;
	Thu, 05 Feb 2015 16:22:08 -0800 (PST)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=1e100.net; s=20130820;
	h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to
	:cc:subject:references:in-reply-to:content-type;
	bh=wNC4jRpJX7Irrbw4dZ/RdJ4lHgJ8tWahIWnBavBQ6vY=;
	b=ct4Km64Yg7aD/hDitJWk8C8qBrxf7I6MgOoETp9/0AQjTdY2l1fwD41XzddxfWLZr7
	1a4EdZZdYaJG6YAYWJQSO+9+FiJ/H7ze/4l+FiT+HuTWxDJCu31P62r3eGqWS++B4mtB
	fHsYkeJ/K27ASeyMQGDGVnOCv8dkWm/OStlxVCF/8rGeohuUCuplQ4+42+INNItMuKsm
	Kw1GHVtjvK5M7rff7HDEGqBn9otuoky+4oAXFCOL022z+/FoUpb0mMrPHZKqES8WlU3v
	zQCUxXsDOk1DjRQsX9I2Dqx6jcwf/9P8Xv10Mbj1J6GXP5r8u5UFq4sUBE+F4RQlu4yj
	hrEQ==
X-Gm-Message-State: ALoCoQm9Yl1oyjt5w9v3TLhj7VicnOpZmH1/pixASq2E6WtyYx8IWi9OG5d7+R1mhUt1KP+/7RDn
X-Received: by 10.68.231.102 with SMTP id tf6mr1300734pbc.40.1423182128081;
	Thu, 05 Feb 2015 16:22:08 -0800 (PST)
Received: from [10.0.1.3] (c-50-135-46-157.hsd1.wa.comcast.net.
	[50.135.46.157])
	by mx.google.com with ESMTPSA id r7sm6145955pdn.87.2015.02.05.16.22.07
	(version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
	Thu, 05 Feb 2015 16:22:07 -0800 (PST)
Message-ID: <54D4093F.5000707@voskuil.org>
Date: Thu, 05 Feb 2015 16:22:23 -0800
From: Eric Voskuil <eric@voskuil.org>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
	rv:31.0) Gecko/20100101 Thunderbird/31.2.0
MIME-Version: 1.0
To: =?UTF-8?B?TeKStnJ0aW4gSOKStmJv4pOLxaF0aWFr?= <martin.habovstiak@gmail.com>
References: <CABdy8DKS4arkkCLGC=66SUJm5Ugib1EWP7B6MkQRX1k-yd3WBw@mail.gmail.com>	<CANEZrP3v=ySS4gragaWuBMWi_swocRRRq_kw2edo6+9kifgrFQ@mail.gmail.com>	<54D3D636.1030308@voskuil.org>	<CANEZrP3ekWQWeV=Yw_E=n0grORBLHaXLUh3w0EFQdz=HsjWvZw@mail.gmail.com>	<279489A5-1E46-48A2-8F58-1A25821D4D96@gmail.com>	<CANEZrP3VAWajxE=mNxb6sLSQbhaQHD=2TgRKvYrEax2PAzCi2A@mail.gmail.com>	<6AEDF3C4-DEE0-4E31-83D0-4FD92B125452@voskuil.org>	<CABdy8DLRGyy5dvmVb_B3vao7Qwz-zdAC3-+2nJkg9rSsU6FLbw@mail.gmail.com>	<C28CD881-DAB8-4EDB-B239-7D45A825EAF0@voskuil.org>	<54D3FB4A.9010105@voskuil.org>	<CALkkCJammCvVd6_1SYRvnxsMVj_x1AvS1VsSa6_76d0NWMDs=Q@mail.gmail.com>	<54D400F0.9090406@voskuil.org>
	<CALkkCJYLfEXxvKjOMCNtK3zhCOmO24JD3w73VwORoqX9xF_p7w@mail.gmail.com>
In-Reply-To: <CALkkCJYLfEXxvKjOMCNtK3zhCOmO24JD3w73VwORoqX9xF_p7w@mail.gmail.com>
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature";
	boundary="TeE7WPtafmTddeI1dUHCKCg636OsGKSoU"
X-Spam-Score: 0.0 (/)
X-Spam-Report: Spam Filtering performed by mx.sourceforge.net.
	See http://spamassassin.org/tag/ for more details.
X-Headers-End: 1YJWgX-0003ac-Pn
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	Paul Puey <paul@airbitz.co>
Subject: Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE)
 transfer of Payment URI
X-BeenThere: bitcoin-development@lists.sourceforge.net
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: <bitcoin-development.lists.sourceforge.net>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
	<mailto:bitcoin-development-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development>
List-Post: <mailto:bitcoin-development@lists.sourceforge.net>
List-Help: <mailto:bitcoin-development-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
	<mailto:bitcoin-development-request@lists.sourceforge.net?subject=subscribe>
X-List-Received-Date: Fri, 06 Feb 2015 00:22:15 -0000

This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
--TeE7WPtafmTddeI1dUHCKCg636OsGKSoU
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable


On 02/05/2015 04:04 PM, M=E2=92=B6rtin H=E2=92=B6bo=E2=93=8B=C5=A1tiak wr=
ote:
> That's exactly what I though when seeing the RedPhone code, but after
> I studied the commit protocol I realized it's actually secure and
> convenient way to do it. You should do that too. :)

I was analyzing the model as you described it to me. A formal analysis
of the security model of a particular implementation, based on inference
from source code, is a bit beyond what I signed up for. But I'm
perfectly willing to comment on your description of the model if you are
willing to indulge me.

> Shortly, how it works:
> The initiator of the connection sends commit message containing the
> hash of his temporary public ECDH part, second party sends back their
> public ECDH part and then initiator sends his public ECDH part in
> open. All three messages are hashed together and the first two bytes
> are used to select two words from a shared dictionary which are
> displayed on the screen of both the initiator and the second party.

> The parties communicate those two words and verify they match.

How do they compare words if they haven't yet established a secure channe=
l?

> If an attacker wants to do MITM, he has a chance of choosing right
> public parts 1:65536. There is no way to brute-force it, since that
> would be noticed immediately. If instead of two words based on the
> first two bytes, four words from BIP39 wordlist were chosen, it would
> provide entropy of 44 bits which I believe should be enough even for
> paranoid people.
>=20
> How this would work in Bitcoin payment scenario: user's phone
> broadcasts his name, merchant inputs amount and selects the name from
> the list, commit message is sent (and then the remaining two
> messages), merchant spells four words he sees on the screen and buyer
> confirms transaction after verifying that words match.

So the assumption is that there exists a secure (as in proximity-based)
communication channel?

e

> 2015-02-06 0:46 GMT+01:00 Eric Voskuil <eric@voskuil.org>:
>> On 02/05/2015 03:36 PM, M=E2=92=B6rtin H=E2=92=B6bo=E2=93=8B=C5=A1tiak=
 wrote:
>>>> A BIP-70 signed payment request in the initial broadcast can resolve=
 the
>>>> integrity issues, but because of the public nature of the broadcast
>>>> coupled with strong public identity, the privacy compromise is much
>>>> worse. Now transactions are cryptographically tainted.
>>>>
>>>> This is also the problem with BIP-70 over the web. TLS and other
>>>> security precautions aside, an interloper on the communication, desk=
top,
>>>> datacenter, etc., can capture payment requests and strongly correlat=
e
>>>> transactions to identities in an automated manner. The payment reque=
st
>>>> must be kept private between the parties, and that's hard to do.
>>>
>>> What about using encryption with forward secrecy? Merchant would
>>> generate signed request containing public ECDH part, buyer would send=

>>> back transaction encrypted with ECDH and his public ECDH part. If
>>> receiving address/amount is meant to be private, use commit protocol
>>> (see ZRTP/RedPhone) and short authentication phrase (which is hard to=

>>> spoof thanks to commit protocol - see RedPhone)?
>>
>> Hi Martin,
>>
>> The problem is that you need to verify the ownership of the public key=
=2E
>> A MITM can substitute the key. If you don't have verifiable identity
>> associated with the public key (PKI/WoT), you need a shared secret (su=
ch
>> as a secret phrase). But the problem is then establishing that secret
>> over a public channel.
>>
>> You can bootstrap a private session over the untrusted network using a=

>> trusted public key (PKI/WoT). But the presumption is that you are
>> already doing this over the web (using TLS). That process is subject t=
o
>> attack at the CA. WoT is not subject to a CA attack, because it's
>> decentralized. But it's also not sufficiently deployed for some scenar=
ios.
>>
>> e
>>


--TeE7WPtafmTddeI1dUHCKCg636OsGKSoU
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJU1Ak/AAoJEDzYwH8LXOFOTtEH/3ZinXCIXzqZi7khNziLXvoV
Eyf0mQoWRi5sXZOez8bJjbB+b1xVfti6SSJht1UyAcB+xVk7pi29VEsIIhq5mppg
OtY7MBAmpIvr7xaVyGXOxi0amCk295VONc/6xTGoElVkADx1HsnGOWEbCYRBvrk0
RlmZpkjWwK/X8g2Zg2P57yMhp6bcQ53bCtMYr6YCC/XxHdn76QI843vUitWVo6Fh
NRsSnTL5oCUHsJNq0glfp0VjcFP5P6XD2J9zX/3FxvIoretLZcspNFksN85gQkg/
Tx01p6dTEkytkuvCuDyZGI7JVdJXIxPQSzvNo7KQ2SssArg3QIR6LwD3ebmVjVM=
=+oYC
-----END PGP SIGNATURE-----

--TeE7WPtafmTddeI1dUHCKCg636OsGKSoU--