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>
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> 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>
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next prev parent 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 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
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