From: Alan Reiner <etotheipi@gmail•com>
To: bitcoin-development@lists•sourceforge.net
Subject: Re: [Bitcoin-development] Is this a safe thing to be doing with ECC addition? (Oracle protocol)
Date: Sat, 08 Mar 2014 18:13:10 -0500 [thread overview]
Message-ID: <531BA406.4070900@gmail.com> (raw)
In-Reply-To: <531AF2EA.50904@gmail.com>
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Note that one of the reasons why this is insecure is because EC point
addition is invertible. EC-scalar multiplication is not, thus why EC
Diffie-Hellman is secure even when this asymmetry exists.
A good cryptosystem doesn't have strange restrictions, like "your public
key can only be public sometimes, but needs to protected like your
private key other times." If you have to worry about things like that,
you're doing it wrong :)
-Alan
On 03/08/2014 05:37 AM, Joel Kaartinen wrote:
> If both parties insist on seeing a hash of the other party's public
> key before they'll show their own public key, they can be sure that
> the public key is not chosen based on the public key they themselves
> presented.
>
> Although, I have to wonder, why not just use multisig?
>
> - Joel
>
> On 08.03.2014 10:51, Edmund Edgar wrote:
>> On 8 March 2014 17:10, Alan Reiner <etotheipi@gmail•com
>> <mailto:etotheipi@gmail•com>> wrote:
>>
>>
>> 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)
>>
>>
>> Thanks Alan and Forrest, that makes sense. So to salvage the
>> situation in the original case, we have to make sure the parties
>> exchange their public keys first, before they're allowed to see the
>> public keys they'll be combining them with.
>>
>> --
>> --
>> Edmund Edgar
>> Founder, Social Minds Inc (KK)
>> Twitter: @edmundedgar
>> Linked In: edmundedgar
>> Skype: edmundedgar
>> http://www.socialminds.jp
>>
>> Reality Keys
>> @realitykeys
>> ed@realitykeys•com <mailto:ed@realitykeys•com>
>> https://www.realitykeys.com
>>
>>
>> ------------------------------------------------------------------------------
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>
>
>
> ------------------------------------------------------------------------------
> Subversion Kills Productivity. Get off Subversion & Make the Move to Perforce.
> With Perforce, you get hassle-free workflows. Merge that actually works.
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> freedom to use Git, Perforce or both. Make the move to Perforce.
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>
>
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next prev parent reply other threads:[~2014-03-08 23:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-08 6:55 Edmund Edgar
2014-03-08 8:10 ` Alan Reiner
2014-03-08 8:51 ` Edmund Edgar
2014-03-08 10:37 ` Joel Kaartinen
2014-03-08 17:41 ` Adam Back
2014-03-08 18:15 ` Natanael
2014-03-08 23:13 ` Alan Reiner [this message]
2014-03-08 20:30 ` Alan Reiner
-- strict thread matches above, loose matches on Subject: below --
2014-03-04 2:59 Edmund Edgar
2014-03-04 5:07 ` Odinn Cyberguerrilla
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