Re: [Ace] Embedded Content Types

"Panos Kampanakis (pkampana)" <> Thu, 21 February 2019 21:32 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id A3AFC131282; Thu, 21 Feb 2019 13:32:21 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -14.501
X-Spam-Status: No, score=-14.501 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, URIBL_BLOCKED=0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id WyfOtMnpqut2; Thu, 21 Feb 2019 13:32:19 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 52C7A131278; Thu, 21 Feb 2019 13:32:19 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=3216; q=dns/txt; s=iport; t=1550784739; x=1551994339; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=SHANmN9FHWxyPQpj/xfUV/WG0n3i7JiyzmA8gOLbpe0=; b=JTNo7dNCibxGmtD+UZjLAK4csAvnivla9pTwSeyrwPMNSrekQtA01zCB J74VeiXmME9+2rNDzY5izEJhzV1X+YcQfNgdP3K6bPY4oeiObxpDaM1Mn SrVxmHeWDJbv0/wsNzw9U+nxKUI3PGxZdALSrKrudcz3RzTb59uOk1X2y 4=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.58,396,1544486400"; d="scan'208";a="240141860"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Feb 2019 21:32:18 +0000
Received: from ( []) by (8.15.2/8.15.2) with ESMTPS id x1LLWIqq019798 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=FAIL); Thu, 21 Feb 2019 21:32:18 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 21 Feb 2019 15:32:17 -0600
Received: from ([]) by ([]) with mapi id 15.00.1395.000; Thu, 21 Feb 2019 15:32:17 -0600
From: "Panos Kampanakis (pkampana)" <>
To: Carsten Bormann <>
CC: Jim Schaad <>, "" <>, "Klaus Hartke" <>, "" <>
Thread-Topic: [Ace] Embedded Content Types
Thread-Index: AdTJQwabXPaUkoDzRkqcz/D5vJfkVwAH1C+AABSNAYAACQoogA==
Date: Thu, 21 Feb 2019 21:32:17 +0000
Message-ID: <>
References: <02a201d4c945$eb10a510$c131ef30$> <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
Archived-At: <>
Subject: Re: [Ace] Embedded Content Types
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Authentication and Authorization for Constrained Environments \(ace\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 21 Feb 2019 21:32:25 -0000

Thanks Carsten. 

Let's say we use a query /skg?sk=xxx&spk=yyy. /skg/xxx,yyy is a different URI imo, so it changes the EST spec and that introduces changes that affect CAs that already implemented it. So let's say we do /skg?sk=xxx&spk=yyy. When I am doing resource discovery and the server is returning the content formats for skg, is he going to signal his supported formats with 
</est/skg>;rt="ace.est.skg";ct="62 xxx yyy"

RFC5272 says
> The Content-Format code "ct" attribute provides a hint about the 
> Content-Formats this resource returns.  Note that this is only a hint, 
> and it does not override the Content-Format Option of a CoAP response 
> obtained by actually requesting the representation of the resource. 
> [...] The Content-Format code attribute MAY include a space-separated 
> sequence of Content-Format codes, indicating that multiple 
> content-formats are available.

So it looks tome that ct="62 280 284 281 TBD287" could hint to the client that all the following formats are supported for the multipart. 

I had a chat with Klaus where he mentioned that he assumed the ct="63 xxx yyy" returned attribute values are the accepted values by the server in the "Accept" option. 

-----Original Message-----
From: Carsten Bormann <> 
Sent: Wednesday, February 20, 2019 8:11 PM
To: Panos Kampanakis (pkampana) <>
Cc: Jim Schaad <>om>;; Klaus Hartke <>de>;
Subject: Re: [Ace] Embedded Content Types

On Feb 20, 2019, at 22:33, Panos Kampanakis (pkampana) <> wrote:
> If we broke the requests to different URIs, it means that a client needs to keep track of his transactions and on top of it he needs to correlate the key and the cert he receives at a later time.

I think this is just a misunderstanding — the idea wasn’t to supply the parts under different URIs, but to make up different URIs for retrieving the different combinations coming in one multipart-core, in one transaction.

As in


(Where sk is short for “secret key” and spk for “signed public key” — substitute your own names.)

or, say


This provides full format agility while preserving the interaction model.

Grüße, Carsten