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Date: Wed, 10 May 2017 06:44:57 +0900
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To: Andrey Andreev <narf@devilix.net>
Cc: Niklas Keller <me@kelunik.com>, Pieter Hordijk <info@pieterhordijk.com>, 
	Joe Watkins <pthreads@pthreads.org>, internals <internals@lists.php.net>, 
	phpdoc <phpdoc@lists.php.net>, Nikita Popov <nikita.ppv@gmail.com>
Content-Type: multipart/alternative; boundary=001a11471d5ebc4fb0054f1e46cb
Subject: Re: [PHP-DEV] [RFC][VOTE] Improve hash_hkdf() parameter
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Content-Type: text/plain; charset=UTF-8

Hi Andrey,

On Sun, Apr 30, 2017 at 8:26 AM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:

> On Sun, Apr 30, 2017 at 8:14 AM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:
>
>> I don't need your view of HKDF RFC or usage, but I do need good practical
>> examples that justify your point of view. Please don't waste of your/my
>> time,
>> just give some good examples in next reply. Thanks.
>>
>
> BTW, valid (yet not common/proper) example that I can think of is,
>
> <?php
> $strong_512bit_key = random_bytes(64);
> $strong_256bit_key = hash_hkdf('sha3-512', $strong_512bit_key, 32);
> ?>
>
> while it does not even require HKDF, though.
>
> <?php
> $strong_512bit_key = random_bytes(64);
> $strong_256bit_key = hash('sha3-256', $strong_512bit_key);
> ?>
>
> should be good enough.
>
> Even with "Info", following HMAC is enough.
>
> <?php
> $strong_512bit_key = random_bytes(64);
> $strong_256bit_key = hash_hmac('sha3-256', $strong_512bit_key, $some_info);
> ?>
>

I'm only asking examples for long enough time.
I presume you cannot think of any valid and good example that
justify current hash_hkdf() signature.

Then documentation must stress not to use hash_hkdf() only with
"length" and "length/info".

Regards,

P.S.
Draft doc patch is this. (Not updated yet)
https://gist.github.com/anonymous/ace4fa267f20041676f265fe58c3f1ea

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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