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From: Jonas Schnelli <dev@jonasschnelli.ch>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] BIP 151 use of HMAC_SHA512
Date: Tue, 28 Jun 2016 09:19:04 +0200	[thread overview]
Message-ID: <577224E8.6070307@jonasschnelli.ch> (raw)
In-Reply-To: <87h9cecad5.fsf@rustcorp.com.au>


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> To quote:
> 
>> HMAC_SHA512(key=ecdh_secret|cipher-type,msg="encryption key").
>>
>>  K_1 must be the left 32bytes of the HMAC_SHA512 hash.
>>  K_2 must be the right 32bytes of the HMAC_SHA512 hash.
> 
> This seems a weak reason to introduce SHA512 to the mix.  Can we just
> make:
> 
> K_1 = HMAC_SHA256(key=ecdh_secret|cipher-type,msg="header encryption key")
> K_2 = HMAC_SHA256(key=ecdh_secret|cipher-type,msg="body encryption key")

SHA512_HMAC is used by BIP32 [1] and I guess most clients will somehow
make use of bip32 features. I though a single SHA512_HMAC operation is
cheaper and simpler then two SHA256_HMAC.

AFAIK, sha256_hmac is also not used by the current p2p & consensus layer.
Bitcoin-Core uses it for HTTP RPC auth and Tor control.

I don't see big pros/cons for SHA512_HMAC over SHA256_HMAC.

</jonas>

[1]
https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#child-key-derivation-ckd-functions


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  parent reply	other threads:[~2016-06-28  7:19 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 ` Jonas Schnelli [this message]
2016-06-28  8:31   ` [bitcoin-dev] BIP 151 use of HMAC_SHA512 Arthur Chen
2016-06-29 18:34     ` Jonas Schnelli
2016-06-29 20:13       ` Peter Todd
2016-06-29 20:31         ` Jonas Schnelli
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

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