To: David Wong <davidwong.crypto@gmail.com>
Cc: cfrg@irtf.org
References: <4cce37d5-e87c-f23d-c1ab-14491a4d764c@science.ru.nl>
 <878e3a08-572a-1fa1-f9f0-0b10f94cc1f0@science.ru.nl>
 <CAK3aN2omFY=LtG5QLCv-CvdoCXxy33aPD_U2yrO7Fe-BgZ37vg@mail.gmail.com>
From: =?UTF-8?Q?Beno=c3=aet_Viguier?= <b.viguier@science.ru.nl>
Message-ID: <2f255eea-903e-93de-7dbb-b1a83f939f6e@science.ru.nl>
Date: Mon, 22 Jan 2018 17:00:13 +0100
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Subject: Re: [Cfrg] KangarooTwelve draft has been updated to 01
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Hi David,

Using their names directly as variables breaks the compactness of the 
writing. cf as follows:

S = M || C || length_encode( |C| ) KangarooTwelve( M, C, L ) = F( 
FinalNode||`07`, L ) KangarooTwelve( M, C, L ) = F( FinalNode||`06`, L )

Also with the same arguments we should expend L.
Also the following text is quite explicit about the meaning of M and C :

KangarooTwelve is an eXtendable Output Function (XOF). It takes as an 
input a couple of byte-strings (M, C) and a positive integer L where M 
byte-string, is the Message and C byte-string, is a OPTIONAL 
Customization string and L positive integer, the number of output bytes 
requested.

In the end those are mainly editorial details.

On 01/22/2018 04:20 PM, David Wong wrote:
>> While the notation X, S by NIST SP - 800-185, I find Message and
>> Customization string easier to remember:
>> variable names should be able to give the reader an idea of what they are
>> about. Also NIST FIPS 180-4 and NIST FIPS 202 uses M for message. However if
>> a majority of people are in favor of (X,S), I don't mind switching for this
>> notation.
> By the way, why not giving them actual names like "custom_string" and "message"?
>
> David

-- 
Kind regards,

Benoît Viguier
Software Engineer - PhD Student | Cryptography & Formal Methods
Radboud University | Mercator 1, room 03.17, Toernooiveld 212
6525 EC Nijmegen, the Netherlands | www.viguier.nl


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    <p>Hi David,<br>
    </p>
    <p>Using their names directly as variables breaks the compactness of
      the writing. cf as follows:</p>
    <font color="#6600cc"> </font>
    <pre class="newpage"><font color="#6600cc">S = M || C || length_encode( |C| )
KangarooTwelve( M, C, L ) = F( FinalNode||`07`, L )
KangarooTwelve( M, C, L ) = F( FinalNode||`06`, L )</font>
</pre>
    Also with the same arguments we should expend L.<br>
    Also the following text is quite explicit about the meaning of M and
    C :<br>
    <pre class="newpage"><font color="#6600cc">KangarooTwelve is an eXtendable Output Function (XOF).  It takes as
   an input a couple of byte-strings (M, C) and a positive integer L
   where

   M  byte-string, is the Message and

   C  byte-string, is a OPTIONAL Customization string and

   L  positive integer, the number of output bytes requested.
</font>

</pre>
    In the end those are mainly editorial details.<br>
    <br>
    <div class="moz-cite-prefix">On 01/22/2018 04:20 PM, David Wong
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAK3aN2omFY=LtG5QLCv-CvdoCXxy33aPD_U2yrO7Fe-BgZ37vg@mail.gmail.com">
      <blockquote type="cite">
        <pre wrap="">While the notation X, S by NIST SP - 800-185, I find Message and
Customization string easier to remember:
variable names should be able to give the reader an idea of what they are
about. Also NIST FIPS 180-4 and NIST FIPS 202 uses M for message. However if
a majority of people are in favor of (X,S), I don't mind switching for this
notation.
</pre>
      </blockquote>
      <pre wrap="">
By the way, why not giving them actual names like "custom_string" and "message"?

David
</pre>
    </blockquote>
    <br>
    <pre class="moz-signature" cols="72">-- 
Kind regards,

Benoît Viguier
Software Engineer - PhD Student | Cryptography &amp; Formal Methods
Radboud University | Mercator 1, room 03.17, Toernooiveld 212
6525 EC Nijmegen, the Netherlands | <a class="moz-txt-link-abbreviated" href="http://www.viguier.nl">www.viguier.nl</a></pre>
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