Re: [CFRG] Extract-and-expand with KMAC

"rsw@jfet.org" <rsw@jfet.org> Wed, 18 November 2020 19:05 UTC

Date: Wed, 18 Nov 2020 11:05:50 -0800
From: "rsw@jfet.org" <rsw@jfet.org>
To: "Dang, Quynh H. (Fed)" <quynh.dang@nist.gov>
Cc: Gilles VAN ASSCHE <gilles.vanassche@st.com>, CFRG <cfrg@irtf.org>
Message-ID: <20201118190550.hzpggpt5a367auik@muon>
References: <467DD0FC-FF7F-453F-98B2-ADC7F0F976B1@ericsson.com> <20201115163535.GA3384456@LK-Perkele-VII> <AM9PR10MB43541E50ABC210C17630FBFCF2E10@AM9PR10MB4354.EURPRD10.PROD.OUTLOOK.COM> <20201118175330.nt4nb4jqvzsjtmjw@muon> <SA0PR09MB68410F90BBD3A5D45FF5E858F3E10@SA0PR09MB6841.namprd09.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <SA0PR09MB68410F90BBD3A5D45FF5E858F3E10@SA0PR09MB6841.namprd09.prod.outlook.com>
Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/ekAEsA2ZNBa_MywLm5Vj8MPW5Gg>
Subject: Re: [CFRG] Extract-and-expand with KMAC
Precedence: list

Hi Quynh,

"Dang, Quynh H. (Fed)" <quynh.dang@nist.gov> wrote:
> I am not aware of a protocol where the output from an extract step:
> PRK is saved and the expansion step gets executed later to generate
> keys.

Totally agreed! in most cases, we don't worry much about PRK. Note,
however, that the message I was responding to explicitly *did* worry
about it:

Gilles VAN ASSCHE <gilles.vanassche@st.com> wrote:
> This solution is not incompatible with the case where an intermediate
> value PRK is required:

If indeed the intermediate value is required, as discussed here, then
my concerns about non--black-box use of the primitives are relevant.
Otherwise, as you say, no worries at all---and we have good reason
to believe that constructions like SHA-3 are great for such cases.

Best,

-=rsw

[CFRG] Extract-and-expand with KMAC John Mattsson
Re: [CFRG] Extract-and-expand with KMAC John Mattsson
Re: [CFRG] Extract-and-expand with KMAC Ilari Liusvaara
Re: [CFRG] Extract-and-expand with KMAC Jonathan Hammell
Re: [CFRG] Extract-and-expand with KMAC Ruggero SUSELLA
Re: [CFRG] Extract-and-expand with KMAC Gilles VAN ASSCHE
Re: [CFRG] Extract-and-expand with KMAC rsw
Re: [CFRG] Extract-and-expand with KMAC Dang, Quynh H. (Fed)
Re: [CFRG] Extract-and-expand with KMAC rsw@jfet.org
Re: [CFRG] Extract-and-expand with KMAC Gilles VAN ASSCHE