Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:97685
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain devilix.net designates 209.85.218.45 as permitted sender)
MIME-Version: 1.0
Date: Wed, 11 Jan 2017 16:24:10 +0200
Message-ID: <CAPhkiZz+eHFEYFA_4yCbTeBZ8KtugbO_Vw9acERo9G+hWYGteQ@mail.gmail.com>
To: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a113debb8bba4110545d25a09
Subject: [Discussion] HKDF
From: narf@devilix.net (Andrey Andreev)

--001a113debb8bba4110545d25a09
Content-Type: text/plain; charset=UTF-8

Hi all,

There's a pending GitHub pull request of mine to include a HKDF
implementation into ext/hash.
Mostly anybody who saw it agreed that it probably doesn't require an RFC
vote, but I hadn't originally announced it here on the list either, so this
is what I'm doing now ...

For technical details, I'd say it is best to read IETF RFC 5869, which
defines it, but here's the TL;DR version:

 - HKDF stands for "HMAC-based Key Derivation Function"
 - Useful in constructing encryption schemes, most notably to derive
separate keys for encryption, authentication using only a single input key.
Unless you're doing that, you probably don't care about it.
 - Unlike e.g. PBKDF2, it is supposed to be fast (as it's not a
password-based KDF), making it great for encryption/decryption on the fly
in web applications

There's one thing that may be contentious - whether to call it hkdf() or
hash_hkdf(); there are valid reasons for both and that's what I'd like to
discuss mostly, as everything else boils down to just a tumbs up/down for
the entire thing. But of course, I appreciate all feedback. :)

GitHub PR: https://github.com/php/php-src/pull/1105
IETF RFC: https://tools.ietf.org/html/rfc5869

P.S.: The PR was submitted a long time ago - almost 2 years - thanks to Joe
for bumping it up.

Cheers,
Andrey.

--001a113debb8bba4110545d25a09--