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From: Erik Aronesty <erik@q32.com>
To: Tier Nolan <tier.nolan@gmail.com>,
	 Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP Number Request: Addresses over Audio
Date: Thu, 11 Aug 2016 16:37:04 -0400	[thread overview]
Message-ID: <CAJowKgL39qFpGAVTkNoUUR7-M2VJxqkQ=X6yK3aTsGLRAo59Jw@mail.gmail.com> (raw)
In-Reply-To: <CAE-z3OU7XgqivsGLXMyd2_cVRE3Kw2FNLGBU261q39=hq9TnEw@mail.gmail.com>

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Can't have shared secrets or interactivity for a public address to have the
love it needs.

Still not sure how you can take a BIP32 public seed and figure out if an
address was derived from it though.   I mean, wouldn't I have to compute
all 2^31 possible public child addresses?





On Thu, Aug 11, 2016 at 11:13 AM, Tier Nolan via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> On Thu, Aug 11, 2016 at 2:55 PM, Erik Aronesty via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>> Sorr, I thought there was some BIP for a public seed such that someone
>> can generate new random addresses, but cannot trivially verify whether an
>> address was derived from the seed.
>>
>
> If you take a public key and multiply it by k, then the recipient can work
> out the private key by multiplying their master private key by k.
>
> If k is random, then the recipient wouldn't be able to work it out, but if
> it is non-random, then everyone else can work it out.  You need some way to
> get k to the recipient without others figuring it out.
>
> This means either the system is interactive or you use a shared secret.
>
> The info about the shared secret is included in the scriptPubKey (or the
> more socially conscientious option, an OP_RETURN).
>
> The address would indicate the master public key.
>
> master_public = master_private * G
>
> The transaction contains k*G.
>
> Both sides can compute the shared secret.
>
> secret = k*master_private*G = master_private*k*G
>
> <encode(k*G)> DROP DUP HASH160 <hash160(encode(secret + pub key))>
> EQUALVERIFY CHECKSIG
>
> This adds 34 bytes to the scriptPubKey.
>
> This is pretty heavy for scanning for transactions sent to you.  You have
> to check every transaction output to see if it is the given template.  Then
> you have to do an ECC multiply to compute the shared secret.  Once you have
> the shared secret, you need to do an ECC addition and a hash to figure out
> if it matches the public key hash in the output.
>
> This is approx one ECC multiply per output and is similar CPU load to what
> you would need to do to actually verify a block.
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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  reply	other threads:[~2016-08-11 20:37 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-08 21:22 [bitcoin-dev] BIP Number Request: Addresses over Audio Daniel Hoffman
2016-08-08 22:06 ` Justin Newton
2016-08-08 22:35   ` Daniel Hoffman
2016-08-08 22:59   ` Trevin Hofmann
2016-08-09  1:50     ` Daniel Hoffman
2016-08-09 23:06       ` Daniel Hoffman
2016-08-10  0:17         ` Jannes Faber
2016-08-10  0:27         ` Chris Riley
2016-08-10  0:36         ` Luke Dashjr
2016-08-10  1:09         ` Thomas Daede
2016-08-10  1:53           ` Daniel Hoffman
2016-08-10  2:14         ` Gregory Maxwell
2016-08-10 10:41           ` Tier Nolan
2016-08-10 11:42             ` Erik Aronesty
2016-08-10 11:49               ` Theo Chino
2016-08-10 16:01                 ` Daniel Hoffman
2016-08-10 17:28                   ` Erik Aronesty
2016-08-10 17:38                     ` Pieter Wuille
2016-08-10 17:55                       ` Daniel Hoffman
2016-08-10 22:31                         ` James MacWhyte
2016-08-11 13:55                       ` Erik Aronesty
2016-08-11 15:13                         ` Tier Nolan
2016-08-11 20:37                           ` Erik Aronesty [this message]
2016-08-12  0:36                             ` Gregory Maxwell
2016-08-12 12:36                               ` Erik Aronesty
2016-08-12 15:49                                 ` Jorge Timón
2016-08-12 18:39                                 ` James MacWhyte
2016-08-13  4:41                                   ` Daniel Hoffman

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