From: Ethan Heilman <eth3rs@gmail•com>
To: Pieter Wuille <pieter.wuille@gmail•com>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 151 use of HMAC_SHA512
Date: Wed, 29 Jun 2016 10:38:43 -0400 [thread overview]
Message-ID: <CAEM=y+X5uT+UbB1f6+ynsWW4ZsxEE4X0-PbHqWXEWz_mUj8Y2w@mail.gmail.com> (raw)
In-Reply-To: <CAPg+sBj3QRGYUzJn96ZS4bf1ZEH9KTwF+OxPXE-O_YJA66grBg@mail.gmail.com>
Just to clarify in BIP-0151 when it says:
>It is important to include the cipher-type into the symmetric cipher key to avoid weak-cipher-attacks.
the cipher-type here refers to the ECDH negotiation parameters?
On Wed, Jun 29, 2016 at 2:58 AM, Pieter Wuille <pieter.wuille@gmail•com> wrote:
> On Jun 29, 2016 07:05, "Ethan Heilman via bitcoin-dev"
> <bitcoin-dev@lists•linuxfoundation.org> wrote:
>>
>> >It's also not clear to me why the HMAC, vs just
>> > SHA256(key|cipher-type|mesg). But that's probably just my crypto
>> > ignorance...
>>
>> SHA256(key|cipher-type|mesg) is an extremely insecure MAC because of
>> the length extension property of SHA256.
>
> This property does technically not apply here, as the output of the hash is
> kept secret, and the possible messages are constants (which are presumably
> chosen in such a way that one is never an extension of another).
>
> However, this is a good example of why you can't generically use a hash
> function in places where you want a MAC (aka "a hash with a shared secret").
> Furthermore, if you already have a hash function anyway, HMAC is very easy
> construct on top of it.
>
> --
> Pieter
next prev parent reply other threads:[~2016-06-29 14:39 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
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 [this message]
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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