Re: [rtcweb] Question about srtp_mki in DTLS/SRTP

Martin Thomson <martin.thomson@gmail.com> Wed, 14 January 2015 01:31 UTC

Return-Path: <martin.thomson@gmail.com>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id DB1661ACE42 for <rtcweb@ietfa.amsl.com>; Tue, 13 Jan 2015 17:31:13 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.7
X-Spam-Level:
X-Spam-Status: No, score=-1.7 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, MIME_8BIT_HEADER=0.3, SPF_PASS=-0.001] autolearn=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id e0QTxy4Y8n8U for <rtcweb@ietfa.amsl.com>; Tue, 13 Jan 2015 17:31:12 -0800 (PST)
Received: from mail-ob0-x235.google.com (mail-ob0-x235.google.com [IPv6:2607:f8b0:4003:c01::235]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 1FAF61B2A1B for <rtcweb@ietf.org>; Tue, 13 Jan 2015 17:31:12 -0800 (PST)
Received: by mail-ob0-f181.google.com with SMTP id gq1so5698189obb.12 for <rtcweb@ietf.org>; Tue, 13 Jan 2015 17:31:11 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=j6R1kH6Y+vjaXciW1baX3cyUWEQvw+bBLMuCSjw0o+s=; b=NNNVp9QSKHT+McTvgxWbqX6nMQFMhhdkSOWZxoKpv3SikqkL0Oh5lps+u5y1iA7i1P 0LKuBLtDeIrUqUeveKNChCjsjf+d3d25y9yPGBOuzwgnccoUx0SgS9OBLSVxPCWt3FW0 XLXO8CWcZSIrdXvCbJl2siy0Q21cQ9UfDQgNePk/rIUrNVzho4vKne41GsncN/mU3wAC ydE3iqIuLWriDHLXcW7s/qkn/9Ou/M2sjbcBAJR3IN+9wjh7nmJLvnZNRZVSBbzrDzwr QD07bDrFzjLRyBSFG8MWn5FNN2GpQOZOFrnBp7aL3JprlRx8ETl/+IdjhD1ZHNr+Pz8Y rEUQ==
MIME-Version: 1.0
X-Received: by 10.182.29.68 with SMTP id i4mr907517obh.30.1421199071438; Tue, 13 Jan 2015 17:31:11 -0800 (PST)
Received: by 10.202.226.136 with HTTP; Tue, 13 Jan 2015 17:31:11 -0800 (PST)
In-Reply-To: <CE6C1F4D-FFA8-4ACA-8807-A624659AECC6@cisco.com>
References: <CAOW+2dvhEzAfyV51p1YWZoc41vih3TKhoArq3CGXzHvSdHEdcA@mail.gmail.com> <CE6C1F4D-FFA8-4ACA-8807-A624659AECC6@cisco.com>
Date: Tue, 13 Jan 2015 17:31:11 -0800
Message-ID: <CABkgnnU58f0-NvS4cy4YL+fT-xH=VzUWW-Z5zNwsy7Nh9xbsDw@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: 🔓Dan Wing <dwing@cisco.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: <http://mailarchive.ietf.org/arch/msg/rtcweb/sjOLWZjfK8NYhrsdmOyPFZbT4Lw>
Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Question about srtp_mki in DTLS/SRTP
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb/>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 14 Jan 2015 01:31:14 -0000

On 13 January 2015 at 17:24, 🔓Dan Wing <dwing@cisco.com> wrote:
> For WebRTC, I don't see SRTP MKI being used.

I'm not aware of anyone using it.  I too would rather prohibit its
use.  That limits two-party session length, but from a practical
perspective, that limit is going to be reached rarely, if ever without
a re-handshake.

Note that EKT isn't a perfect replacement because we should be
prohibiting the initiation of EKT from browser endpoints (well,
applications shouldn't be able to set the value used, though I guess
they could request that the browser initiate EKT).