public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: Jonas Schnelli <dev@jonasschnelli.ch>
To: Peter Todd <pete@petertodd.org>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 151 use of HMAC_SHA512
Date: Wed, 29 Jun 2016 22:31:50 +0200	[thread overview]
Message-ID: <57743036.5040304@jonasschnelli.ch> (raw)
In-Reply-To: <20160629201317.GA4855@fedora-21-dvm>


[-- Attachment #1.1: Type: text/plain, Size: 1188 bytes --]

> On Wed, Jun 29, 2016 at 08:34:06PM +0200, Jonas Schnelli via bitcoin-dev wrote:
>>> Based on previous crypto analysis result, the actual security of SHA512
>>> is not significantly higher than SHA256.
>>> maybe we should consider SHA3?
>>
>> As far as I know the security of the symmetric cipher key mainly depends
>> on the PRNG and the ECDH scheme.
>>
>> The HMAC_SHA512 will be used to "drive" keys from the ECDH shared secret.
>> HMAC_SHA256 would be sufficient but I have specified SHA512 to allow to
>> directly derive 512bits which allows to have two 256bit keys with one
>> HMAC operation (same pattern is used in BIP for the key/chaincode
>> derivation).
> 
> What's the rational for doing that "directly" rather than with two SHA256
> operations? (specifcially SHA256(0 . thing), SHA256(1 + thing) for the two
> parts we need to derive)

SHA256 and SHA512 are both from the SHA-2 family.

I have specified SHA512 to (slightly) increase the brute-force security
of the ecdh shared secret when knowing K_1 and K_2.

And I assumed (haven't measured the required cpu cycles) that a single
SHA512_HMAC is less expensive then two SHA256_HMAC.

</jonas>


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

  reply	other threads:[~2016-06-29 20:31 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-28  2:31 [bitcoin-dev] BIP 151 use of HMAC_SHA512 Rusty Russell
2016-06-28  7:17 ` [bitcoin-dev] BIP 151 Eric Voskuil
2016-06-28  8:26   ` Jonas Schnelli
2016-06-28 16:45     ` Eric Voskuil
2016-06-28 18:22       ` Peter Todd
2016-06-28 18:35         ` Eric Voskuil
2016-06-28 20:14           ` Peter Todd
2016-06-28 20:29             ` Eric Voskuil
2016-06-28 20:36               ` Peter Todd
2016-06-28 21:22                 ` Eric Voskuil
2016-06-28 21:36                   ` Gregory Maxwell
2016-06-28 21:40                     ` Cameron Garnham
2016-06-28 22:07                       ` Eric Voskuil
2016-06-28 22:33                         ` Cameron Garnham
2016-06-28 23:29                           ` Eric Voskuil
2016-06-29  0:06                             ` Nick ODell
2016-06-28 21:59                     ` Eric Voskuil
     [not found]                       ` <CAAS2fgQ0Ocs8hF+pf+fWfkKKhQwxNKpY=JHpb_bwua7neVO8tg@mail.gmail.com>
2016-06-28 23:34                         ` Eric Voskuil
2016-06-28 20:06       ` Jonas Schnelli
2016-06-28 23:31         ` Eric Voskuil
2016-06-29 11:17       ` Alfie John
2016-06-30 11:56         ` Eric Voskuil
2016-06-30 12:20           ` Jonas Schnelli
2016-06-30 12:27             ` Eric Voskuil
2016-06-30 12:43               ` Jonas Schnelli
2016-06-30 15:22                 ` Eric Voskuil
2016-06-30 16:52                   ` Peter Todd
2016-06-30 18:25                     ` Eric Voskuil
2016-06-30 19:06                       ` Peter Todd
2016-06-30 20:26                         ` Eric Voskuil
2016-06-28 19:55     ` Gregory Maxwell
2016-06-28 23:33       ` Eric Voskuil
2016-06-29  1:01         ` Gregory Maxwell
2016-06-30  9:57           ` Eric Voskuil
2016-06-30 13:03             ` Pieter Wuille
2016-06-30 15:10               ` Eric Voskuil
2016-08-31 14:29                 ` Pieter Wuille
2016-06-30 13:36             ` Erik Aronesty
2016-06-30 14:47               ` Alfie John
2016-07-02  9:44               ` Chris Priest
2016-06-28 12:13   ` Jonas Schnelli
2016-06-28 17:39     ` Eric Voskuil
2016-06-28  7:19 ` [bitcoin-dev] BIP 151 use of HMAC_SHA512 Jonas Schnelli
2016-06-28  8:31   ` Arthur Chen
2016-06-29 18:34     ` Jonas Schnelli
2016-06-29 20:13       ` Peter Todd
2016-06-29 20:31         ` Jonas Schnelli [this message]
2016-06-29  1:00   ` Rusty Russell
2016-06-29  1:38     ` Arthur Chen
2016-06-29  1:56     ` Ethan Heilman
2016-06-29  6:58       ` Pieter Wuille
2016-06-29 14:38         ` Ethan Heilman
2016-06-29 18:46           ` Jonas Schnelli
2016-07-01  3:25       ` Rusty Russell
2016-07-01 22:42         ` Zooko Wilcox
2016-07-04  1:23           ` Arthur Chen
2016-07-04  1:44             ` Arthur Chen
2016-07-04  6:47               ` Jonas Schnelli
2016-07-04  6:37           ` Jonas Schnelli

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=57743036.5040304@jonasschnelli.ch \
    --to=dev@jonasschnelli.ch \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    --cc=pete@petertodd.org \
    /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