From: Alan Reiner <etotheipi@gmail•com>
To: timo.hanke@web•de
Cc: Bitcoin Dev <bitcoin-development@lists•sourceforge.net>
Subject: Re: [Bitcoin-development] Optional "wallet-linkable" address format - Payment Protocol
Date: Wed, 19 Jun 2013 10:39:04 -0400 [thread overview]
Message-ID: <51C1C288.4000305@gmail.com> (raw)
In-Reply-To: <20130619142510.GA17239@crunch>
On 06/19/2013 10:25 AM, Timo Hanke wrote:
> Since you mention to use this in conjunction with the payment protocol,
> note the following subtlety. Suppose the payer has to paid this address
> called "destination":
>> Standard Address ~ Base58(0x00 || hash160(PubKeyParent * Multiplier[i]) ||
>> checksum)
> Also suppose the payee has spent the output, i.e. the pubkey
> corresponding to "destination", which is PubKeyParent * Multiplier[i],
> is publicly known. Then anybody can (in retrospect) create arbitrary
> many pairs {PublicKeyParent, Multiplier} (in particular different
> PublicKeyParent) that lead to the same "destination".
>
> Depending on what you have in mind that the transaction should "prove"
> regarding its actual receiver or regarding the receiver's PubKeyParent,
> this could be an unwanted feature (or it could be just fine). If it is
> unwanted then I suggest replacing
> PubKeyParent * Multiplier[i] by
> PubKeyParent * HMAC(Multiplier[i],PubKeyParent)
> which eliminates from the destination all ambiguity about PubKeyParent.
>
> This modification would not be directly compatible with BIP32 anymore
> (unfortunately), but seems to be better suited for use in conjunction
> with a payment protocol.
>
> Timo
It's an interesting observation, but it looks like the most-obvious
attack vector is discrete log problem: spoofing a relationship between
a target public key and one that you control. For instance, if you see
{PubA, Mult} produces PubB and you have PubC already in your control
that you want to "prove" [maliciously] is related to PubB, then you have
to find the multiplier, M that solves: M*PubC = PubB. That's a
discrete logarithm problem.
I'm not as familiar as you are, with the available operations on
elliptic curves, but it sounds like you can produce essentially-random
pairs of {PubX, Mult} pairs that give the same PubB, but you won't have
the private key associated with those public keys. It's an interesting
point, and there may be a reason to be concerned about it. Though, I
don't see it yet.
-Alan
next prev parent reply other threads:[~2013-06-19 14:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-18 3:48 Alan Reiner
2013-06-19 12:19 ` Melvin Carvalho
2013-06-19 13:37 ` Alan Reiner
2013-06-19 13:54 ` Pieter Wuille
2013-06-19 14:25 ` Timo Hanke
2013-06-19 14:39 ` Alan Reiner [this message]
2013-06-19 15:28 ` Adam Back
2013-06-19 18:36 ` Adam Back
2013-06-19 19:00 ` Alan Reiner
2013-06-20 7:48 ` Timo Hanke
2013-06-20 9:10 ` Jeremy Spilman
2013-06-20 16:09 ` Alan Reiner
2013-06-19 20:03 ` Timo Hanke
2013-06-19 19:29 Jeremy Spilman
2013-06-19 20:10 ` Alan Reiner
2013-06-19 21:58 ` Jeremy Spilman
2013-06-19 22:47 ` Alan Reiner
2013-06-20 3:54 ` Jeremy Spilman
2013-06-20 7:32 ` Mike Hearn
2013-06-26 15:29 ` Alan Reiner
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