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Re: [TLS] adopted: draft-ghedini-tls-certificate-compression

mrex@sap.com (Martin Rex) Wed, 07 June 2017 20:51 UTC

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To: Ilari Liusvaara <ilariliusvaara@welho.com>
Date: Wed, 07 Jun 2017 22:50:56 +0200
CC: Raja ashok <raja.ashok@huawei.com>, "draft-ghedini-tls-certificate-compression@ietf.org" <draft-ghedini-tls-certificate-compression@ietf.org>, "<tls@ietf.org>" <tls@ietf.org>
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From: mrex@sap.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/2KLTTcyb2sUoz0NCFrWcrnXSknE>
Subject: Re: [TLS] adopted: draft-ghedini-tls-certificate-compression
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Ilari Liusvaara wrote:
>On Wed, Jun 07, 2017 at 05:38:59AM +0000, Raja ashok wrote:
>> Hi Victor & Alessandro,
>> 
>> I have gone through the draft and I am having a doubt. 
>> 
>>>   The extension only affects the Certificate message from the server.
>>>   It does not change the format of the Certificate message sent by the
>>>   client.
>> 
>> This draft provides a mechanism to compress only the server certificate
>> message, not the client certificate message. I feel client authentication
>> is not performed in HTTPS of web application. But in all other applications
>> (eg. Wireless sensor network) certificate based client authentication is
>> more important. 
>> 
>> So I suggest we should consider compression on client certificate message
>> also.
> 
> Doing client certificate compression would add some complexity, because
> the compression indication currently needs to be external to certificates,
> and there is no place to stick such indication for client certificate.

A TLS extension could do this indication just fine.


ASN.1 DER encoded X.509v3 certificates all have the same first 12 bits.

0x30 0x8*

So sending an indication inband should also be possible.
But a negotiated TLS extension (proposed by client in ClientHello,
confirmed by server in ServerHello) could also change the Certificate PDU
to provide room for a seperate indicator.


-Martin

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