Re: [IPsec] Fw: Preshared key authentication in IKEv2

"Valery Smyslov" <> Mon, 02 November 2009 14:40 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 5C0413A6885 for <>; Mon, 2 Nov 2009 06:40:33 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -0.627
X-Spam-Status: No, score=-0.627 tagged_above=-999 required=5 tests=[AWL=-1.000, BAYES_20=-0.74, J_CHICKENPOX_36=0.6, XMAILER_MIMEOLE_OL_7533E=0.513]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id Ots8bUW9SrGD for <>; Mon, 2 Nov 2009 06:40:32 -0800 (PST)
Received: from ( []) by (Postfix) with ESMTP id D1E2F3A6817 for <>; Mon, 2 Nov 2009 06:40:31 -0800 (PST)
Received: by ewy18 with SMTP id 18so4451792ewy.43 for <>; Mon, 02 Nov 2009 06:40:47 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=gamma; h=domainkey-signature:received:received:message-id:from:to:cc :references:subject:date:mime-version:content-type :content-transfer-encoding:x-priority:x-msmail-priority:x-mailer :x-mimeole; bh=tP48V8DYFx+4tWHYDeeq01mIRHx6ga4rvuy+q0Ep9xg=; b=Y99/dg1FMwAm1dzBxUOidtGrT4S366DFxSsZyCa4eqBaoVP6+vmp5Rjdi9cNIBSB60 da+rjxqaMfc26J4csLpe/SlDjvSVTIDBL3jSSLWKmG4NKvb07vcKvmyQW6vTmDrTnFy2 6B2w9NNHb+gx/OW8Cgrj9VDOCWyquraEztD/o=
DomainKey-Signature: a=rsa-sha1; c=nofws;; s=gamma; h=message-id:from:to:cc:references:subject:date:mime-version :content-type:content-transfer-encoding:x-priority:x-msmail-priority :x-mailer:x-mimeole; b=MUixWhA8y31JRivBw7+/LJHKSwD8F2grd2WcMrUzNe8nCSDk3KW4gUchQJUCP2ewNr NsIPf/wFqVAjU5Uf49gSwiUp1u4BSaPbrAiVX+T77++LcqGT5ZfBKzQJK24XyvPiFgLS shwBG1GGU/GDz9EGYBSL0Gea2L7WxjDHqE0ws=
Received: by with SMTP id k6mr4731834wef.89.1257172846980; Mon, 02 Nov 2009 06:40:46 -0800 (PST)
Received: from svanpc ([]) by with ESMTPS id 10sm15368657eyz.43.2009. (version=SSLv3 cipher=RC4-MD5); Mon, 02 Nov 2009 06:40:45 -0800 (PST)
Message-ID: <>
From: "Valery Smyslov" <>
To: "Tero Kivinen" <>, "Paul Hoffman" <>
References: <><p06240896c710cc6eae34@[]> <>
Date: Mon, 2 Nov 2009 17:40:57 +0300
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 5.50.4963.1700
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4963.1700
Subject: Re: [IPsec] Fw: Preshared key authentication in IKEv2
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Discussion of IPsec protocols <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Mon, 02 Nov 2009 14:40:33 -0000

Hi Paul and Tero,

thank you for your answers.

> > The PRF (or set of PRFs) is known by the receiving party. If the two
> > parties always only use one PRF, it is known. The padding is not a
> > universal solution for the reasons you give, but it works in the
> > common case of peers who know each other's crypto choices.
> As Paul said recipient knows which algorithms it support, and it can

Sometimes it doesn't. I refer to implementations with pluggable
crypto, when crypto providers are separated from IKE implementation
and can be added/removed later.

> store the pre-shared key using all of those algoritms to its database.
> I.e. if it supports PRF_HMAC_SHA1, and PRF_AES128_XCBC then it needs
> to calculate the PRF(Shared Secret, "Key Pad for IKEv2") using those
> two PRFs and store both of the results to its authentication database.

With this approach in case of pluggable crypto user must re-enter shared
after any change in crypto configuration. It's not a big deal, just a bit

Smyslov Valery.