[quicwg/base-drafts] Encrypting Retry token (#3274)

Martin Thomson <notifications@github.com> Wed, 27 November 2019 07:45 UTC

Return-Path: <noreply@github.com>
X-Original-To: quic-issues@ietfa.amsl.com
Delivered-To: quic-issues@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id 484B5120836 for <quic-issues@ietfa.amsl.com>; Tue, 26 Nov 2019 23:45:34 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -8
X-Spam-Status: No, score=-8 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=github.com
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id vicyLV3a_UQp for <quic-issues@ietfa.amsl.com>; Tue, 26 Nov 2019 23:45:32 -0800 (PST)
Received: from out-17.smtp.github.com (out-17.smtp.github.com []) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 97A501207FE for <quic-issues@ietf.org>; Tue, 26 Nov 2019 23:45:32 -0800 (PST)
Date: Tue, 26 Nov 2019 23:45:31 -0800
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=github.com; s=pf2014; t=1574840731; bh=CqCJU2PEF+9fNCnuL/bDcXZkL2rta/tXRV6Hv/hqUVc=; h=Date:From:Reply-To:To:Cc:Subject:List-ID:List-Archive:List-Post: List-Unsubscribe:From; b=Vav28Bk+axV6rFHbi9n+Re4PP6V0RP/tr/GMdzWZoNwrlPoc+H+xh2NGw+udr6uoy SvB/21xL3vxE2LAXpzAOqEyFCegMPi7UDzcF+i94idzPPNwYpDIL9P810t+eYQIJSq VZBFGMQcG3LuIvdXhNT9Lh5RUCqj4yu2FmBxI2/8=
From: Martin Thomson <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+AFTOJK65XHRT7EFPTQAXFA535NOBXEVBNHHB7CUNWA@reply.github.com>
To: quicwg/base-drafts <base-drafts@noreply.github.com>
Cc: Subscribed <subscribed@noreply.github.com>
Message-ID: <quicwg/base-drafts/issues/3274@github.com>
Subject: [quicwg/base-drafts] Encrypting Retry token (#3274)
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5dde299bc5403_66373f8d6e6cd9605295db"; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: list
X-GitHub-Sender: martinthomson
X-GitHub-Recipient: quic-issues
X-GitHub-Reason: subscribed
X-Auto-Response-Suppress: All
X-GitHub-Recipient-Address: quic-issues@ietf.org
Archived-At: <https://mailarchive.ietf.org/arch/msg/quic-issues/ItjF1iOZI3WsW3hIDaMQ5EjGnS8>
X-BeenThere: quic-issues@ietf.org
X-Mailman-Version: 2.1.29
List-Id: Notification list for GitHub issues related to the QUIC WG <quic-issues.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/quic-issues>, <mailto:quic-issues-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/quic-issues/>
List-Post: <mailto:quic-issues@ietf.org>
List-Help: <mailto:quic-issues-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/quic-issues>, <mailto:quic-issues-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 27 Nov 2019 07:45:34 -0000

In Singapore, we reached an impasse regarding the use of encryption on Retry.

>From that discussion, there were two outcomes considered:

* "encrypt" using a fixed key and nonce and don't encrypt the token; put the original destination connection ID in the AAD along with the entire packet

* encrypt the token using the fixed key and a nonce that takes the first 8 bytes of the original destination connection ID; the AAD only includes the connection IDs and version

The first can be reduced to running GHASH with a fixed XOR on the final tag if you really want to save effort.  I've implemented and measured that.

The second can be implemented naively, just by building a new AES key for every record.  That's not terribly slow at 2.8x slower.  With some nasty tricks, I was able to get the AES version under 1.7x slower.  Given the relative cost of these functions, I think that this is an acceptable cost.

There's no guarantee that this is correct - I haven't even checked that these programs produce the right output, but the count of operations is approximately right, so I'm posting this issue.  My code can be found at [martinthomson/quic-retry-tag](https://github.com/martinthomson/quic-retry-tag/blob/master/bench.c) in case reproduction or validation thrills you.

Here's the output of a sample run on my old machine with about 1Mb of Retry packets fed through the different implementations, which takes about 32 seconds to complete:

Measuring best of 1000 iterations
ghash:          22450242
aes_gcm_slow:   60070152
aes_gcm_fast:   35240211

Now, obviously this is a microbenchmark.  The rest of the cost will be elsewhere, but I tried to isolate the variable.  Hopefully this helps the decision-making process.

You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub: