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From: Peter Todd <pete@petertodd.org>
To: Jeremy Spilman <jeremy@taplink.co>
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Stealth Addresses
Date: Mon, 20 Jan 2014 06:08:47 -0500	[thread overview]
Message-ID: <20140120110847.GF3468@savin> (raw)
In-Reply-To: <52F8B4EC-F955-46E4-B871-3BEEFF69907D@taplink.co>

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On Sat, Jan 18, 2014 at 05:12:58PM -0600, Jeremy Spilman wrote:
> 
> 
> > On Fri, Jan 17, 2014 at 8:55 PM, Alan Reiner <etotheipi@gmail.com> wrote:
> >> Isn't there a much faster asymmetric scheme that we can use?  I've heard people talk about ed25519, though I'm not sure it can be used for encryption.
> > 
> > Doing ECDH with our curve is within a factor of ~2 of the fastest
> > encryption available at this security level, AFAIK.  And separate
> > encryption would ~double the amount of data vs using the ephemeral key
> > for derivation.
> > 
> > Using another cryptosystem would mandate carry around additional code
> > for a fast implementation of that cryptosystem, which wouldn't be
> > fantastic.
> > 
> > So I'm not sure much can be improved there.
> 
> In the case where payment is being sent only to Q1, and Q2 is for discovery only, perhaps we could use a 160-bit curve for d2/Q2 and e/P resulting in 20 byte vs 32 bytes in the OP_RETURN, and of course faster multiplication. 
> 
> 80-bits of security I assume still greatly exceeds the actual level of privacy you get with the overall solution, and since Q2 is never protecting actual funds...
> 
> But if it's a "real weakening" of the privacy then definitely not worth it, and even the added complexity of another curve seems possibly not worth it...

Keep in mind that Bitmessage uses the same ECDH mechanism as what
stealth addresses will use. They seem to get decent enough performance
from it for a use-case not-unlike that of a Bitcoin wallet.

In any case I'm interested in knowing actual performance numbers for it;
last I talked to Kyle Drake he said he was working on getting ECDH
numbers on Javascript, probably the slowest possible implementation of
the idea. As for send to stealth addresses using prefixes, he's
confirmed that you'll be able to do that will well under a second to
brute-force the prefixes with the proposed OP_RETURN mechanism even with
rather long 8-bit prefixes.

-- 
'peter'[:-1]@petertodd.org
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  parent reply	other threads:[~2014-01-20 11:09 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-06 12:03 [Bitcoin-development] Stealth Addresses Peter Todd
2014-01-08 10:20 ` Jeremy Spilman
2014-01-10 10:20   ` Peter Todd
2014-01-10 11:28     ` Drak
2014-01-10 12:00       ` Peter Todd
2014-01-12 10:33     ` Jeremy Spilman
2014-01-12 12:51       ` Mike Hearn
2014-01-12 18:20         ` Jeremy Spilman
2014-01-12 18:26           ` Mike Hearn
2014-01-13  9:13             ` Jeremy Spilman
2014-01-14 14:15               ` Peter Todd
2014-01-14 17:54                 ` Odinn Cyberguerrilla
2014-01-12 21:18       ` Gavin Andresen
2014-01-13  9:52         ` Gregory Maxwell
2014-01-13 10:39           ` Mike Hearn
2014-01-13 13:37             ` Roy Badami
2014-01-13 15:58               ` Mike Hearn
2014-01-13 20:11                 ` Roy Badami
2014-01-14 22:53                 ` Roy Badami
2014-01-15  0:19                   ` Drak
2014-01-15 20:22                     ` Ben Davenport
2014-01-15 20:38                       ` Gregory Maxwell
2014-01-15 20:44                         ` Jeff Garzik
2014-01-15 22:38                           ` [Bitcoin-development] Static addresses on chains encouraging address *RE* use Troy Benjegerdes
2014-01-15 23:01                           ` [Bitcoin-development] Stealth Addresses Mike Hearn
2014-01-15 23:04                           ` Roy Badami
2014-01-15 23:07                             ` Jeff Garzik
2014-01-15 23:17                               ` Roy Badami
2014-01-15 23:19                                 ` Roy Badami
2014-01-15 23:09                           ` [Bitcoin-development] unlinakble static address? & spv-privacy (Re: Stealth Addresses) Adam Back
2014-01-16  1:02                             ` Jeremy Spilman
2014-01-16  1:32                               ` Gregory Maxwell
2014-01-18 17:44                                 ` Troy Benjegerdes
2014-01-18 20:25                                   ` Christophe Biocca
2014-01-20 11:11                                   ` Peter Todd
2014-01-21  4:00                                 ` Jeremy Spilman
2014-01-24  9:17                                   ` Peter Todd
2014-01-16 11:42                               ` Adam Back
2014-01-16 18:19                                 ` Troy Benjegerdes
2014-01-16  0:05                           ` [Bitcoin-development] Stealth Addresses Jeremy Spilman
2014-01-16  0:10                             ` Gregory Maxwell
2014-01-16  0:24                             ` Mark Friedenbach
2014-01-16  0:44                             ` Eric Martindale
2014-01-16  6:26                               ` Gary Rowe
2014-01-16  9:48                                 ` Wladimir
2014-01-16  1:16                             ` Odinn Cyberguerrilla
2014-01-16 10:14                             ` Drak
2014-01-16 10:19                               ` Mike Hearn
2014-01-16 11:12                               ` [Bitcoin-development] reusable address privacy problems & fuzzy bait limitations (Re: Stealth Addresses) Adam Back
2014-01-16 21:28                             ` [Bitcoin-development] Stealth Addresses Peter Todd
2014-01-17  2:30                               ` Johnathan Corgan
2014-01-17  3:13                               ` Jeremy Spilman
2014-01-17  7:49                               ` Drak
2014-01-17  9:15                                 ` Mike Hearn
2014-01-17  9:19                                   ` Mark Friedenbach
2014-01-17  9:23                                   ` Natanael
2014-01-17  9:59                                   ` Drak
2014-01-17 20:16                                     ` Cameron Garnham
2014-01-17 14:46                                   ` Peter Todd
2014-01-17 19:21                                     ` Ben Davenport
2014-01-18  4:55                                       ` Alan Reiner
2014-01-18  5:09                                         ` Gregory Maxwell
2014-01-18 23:12                                           ` Jeremy Spilman
2014-01-18 23:50                                             ` Gregory Maxwell
2014-01-20 11:08                                             ` Peter Todd [this message]
2014-01-13 19:53               ` Roy Badami
2014-01-13 19:57                 ` Mike Hearn
2014-01-13 20:01                   ` Roy Badami
2014-01-13 19:40           ` Roy Badami
2014-01-13 19:44             ` Drak
2014-01-13 19:59               ` Alan Reiner
2014-01-13 20:10                 ` Gregory Maxwell
2014-01-13 20:15                   ` Peter Todd
2014-01-13 22:02                   ` Jeremy Spilman
2014-01-14 14:19                     ` Peter Todd
2014-01-14 19:12                       ` Jeremy Spilman
2014-01-14 20:48                         ` Peter Todd
2014-01-14 21:51                         ` Adam Back
2014-01-14 22:34                           ` Jeremy Spilman
2014-01-13 20:14                 ` Peter Todd
2014-01-13 20:41                   ` Alan Reiner
2014-01-13 20:47                     ` Gregory Maxwell
2014-01-13 21:02                     ` Roy Badami
2014-01-13 21:15                       ` Alan Reiner
2014-01-13 21:27                         ` Peter Todd
     [not found]                           ` <op.w9ne31oqyldrnw@laptop-air.hsd1.ca.comcast.net>
2014-01-14 12:10                             ` Peter Todd
2014-03-06 12:23 ` Dan Carter
     [not found] <mailman.417890.1389952750.21953.bitcoin-development@lists.sourceforge.net>
2014-01-17 12:16 ` joseph

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