Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:97786
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.161.170 as permitted sender)
MIME-Version: 1.0
Sender: jakub.php@gmail.com
In-Reply-To: <CAPhkiZz+eHFEYFA_4yCbTeBZ8KtugbO_Vw9acERo9G+hWYGteQ@mail.gmail.com>
References: <CAPhkiZz+eHFEYFA_4yCbTeBZ8KtugbO_Vw9acERo9G+hWYGteQ@mail.gmail.com>
Date: Mon, 16 Jan 2017 11:44:38 +0000
Message-ID: <CAEKnhAE=0qVgNaCKAdbODP1C5PWyTvXL-PP3mBptfq3qamozcQ@mail.gmail.com>
To: Andrey Andreev <narf@devilix.net>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=94eb2c0b605261695e054634b553
Subject: Re: [PHP-DEV] [Discussion] HKDF
From: bukka@php.net (Jakub Zelenka)

--94eb2c0b605261695e054634b553
Content-Type: text/plain; charset=UTF-8

On Wed, Jan 11, 2017 at 2:24 PM, Andrey Andreev <narf@devilix.net> wrote:

> 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();
>

Should be definitely hash_hkdf as it's part of the hash extension (that's
why hash prefix) and we might add openssl_hkdf that will use OpenSSL
implementation added to 1.1 - it would also use OpenSSL implemention for
underlaying hash implementation that is more powerful in some ways (e.g.
ASM optimization of some main hash functions).

Cheers

Jakub

--94eb2c0b605261695e054634b553--