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 ) id 1WMCLI-0002Xi-CT for bitcoin-development@lists.sourceforge.net; Sat, 08 Mar 2014 08:10:48 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.216.176 as permitted sender) client-ip=209.85.216.176; envelope-from=etotheipi@gmail.com; helo=mail-qc0-f176.google.com; Received: from mail-qc0-f176.google.com ([209.85.216.176]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WMCLG-0001XZ-Lm for bitcoin-development@lists.sourceforge.net; Sat, 08 Mar 2014 08:10:48 +0000 Received: by mail-qc0-f176.google.com with SMTP id m20so5848541qcx.35 for ; Sat, 08 Mar 2014 00:10:41 -0800 (PST) X-Received: by 10.224.71.209 with SMTP id i17mr26951094qaj.29.1394266241261; Sat, 08 Mar 2014 00:10:41 -0800 (PST) Received: from [192.168.1.85] (c-76-111-96-126.hsd1.md.comcast.net. [76.111.96.126]) by mx.google.com with ESMTPSA id 30sm16638305qgt.4.2014.03.08.00.10.40 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 08 Mar 2014 00:10:40 -0800 (PST) Message-ID: <531AD080.40501@gmail.com> Date: Sat, 08 Mar 2014 03:10:40 -0500 From: Alan Reiner User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: bitcoin-development@lists.sourceforge.net References: In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: multipart/alternative; boundary="------------010407060002090009010908" X-Spam-Score: -0.6 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (etotheipi[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1WMCLG-0001XZ-Lm Subject: Re: [Bitcoin-development] Is this a safe thing to be doing with ECC addition? (Oracle protocol) X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 08 Mar 2014 08:10:48 -0000 This is a multi-part message in MIME format. --------------010407060002090009010908 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 03/08/2014 01:55 AM, Edmund Edgar wrote: > On 4 March 2014 14:07, Odinn Cyberguerrilla > > wrote: > > Nothing is safe. > > > This is true. To rephrase, imagine I gave you an ECC public key > , you gave me back a public key of your own > devising, then I paid some money to the address resulting from > add_pubkeys(,) [1]. Can anyone either: > > a) Think of a way that Odinn could make an such that they > could spend the resulting money without having . > b) Opine, somewhat knowledgeably, that this probably wouldn't be an > easy thing to do, and they wouldn't be alarmed to see people running > software that did this kind of thing. > > [1] https://github.com/vbuterin/pybitcointools/blob/master/pybitcointools/main.py#L173 Consider that I see your public key before I create and send you my public key . I create a new keypair, with which I know (it can be any arbitrary key pair). But I don't give you , I give you = minus (which I can do because I've seen before doing this). Sure, I don't know the private key for , but it doesn't matter... because what + = (mine) You have no way to detect this condition, because you don't know what c_pub/c_priv I created, so you can only detect this after it's too late (after I abuse the private key) -Alan --------------010407060002090009010908 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 03/08/2014 01:55 AM, Edmund Edgar wrote:
On 4 March 2014 14:07, Odinn Cyberguerrilla <odinn.cyberguerrilla@riseup.net> wrote:
Nothing is safe.

This is true. To rephrase, imagine I gave you an ECC public key <ed_pub>, you gave me back a public key <odinn_pub> of your own devising, then I paid some money to the address resulting from add_pubkeys(<ed_pub>,<odinn_pub>) [1]. Can anyone either:

a) Think of a way that Odinn could make an <odinn_pub> such that they could spend the resulting money without having <ed_priv>.
b) Opine, somewhat knowledgeably, that this probably wouldn't be an easy thing to do, and they wouldn't be alarmed to see people running software that did this kind of thing.


Consider that I see your public key <a_pub> before I create and send you my public key <b_pub>.

I create a new keypair, <c_pub> with <c_priv> which I know (it can be any arbitrary key pair).  But I don't give you <c_pub>, I give you  <b_pub> = <c_pub> minus <a_pub> (which I can do because I've seen <a_pub> before doing this). 

Sure, I don't know the private key for <b_pub>, but it doesn't matter... because what

<b_pub> + <a_pub> = <c_pub> (mine)

You have no way to detect this condition, because you don't know what c_pub/c_priv I created, so you can only detect this after it's too late (after I abuse the private key)

-Alan
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