public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
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



  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 [Bitcoin-development] Optional "wallet-linkable" address format - Payment Protocol 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=51C1C288.4000305@gmail.com \
    --to=etotheipi@gmail.com \
    --cc=bitcoin-development@lists.sourceforge.net \
    --cc=timo.hanke@web.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox