Re: [TLS] Certificate compression draft

Eric Rescorla <ekr@rtfm.com> Wed, 05 April 2017 14:22 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 5 Apr 2017 07:21:47 -0700
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To: Ryan Sleevi <ryan-ietftls@sleevi.com>
Cc: Sankalp Bagaria <sankalp@cdac.in>, R Balaji <balaji@cdac.in>, "tls@ietf.org" <tls@ietf.org>, "Bagaria, Sankalp" <sankalp.nitt@gmail.com>
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Subject: Re: [TLS] Certificate compression draft
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On Wed, Apr 5, 2017 at 7:12 AM, Ryan Sleevi <ryan-ietftls@sleevi.com> wrote:

>
>
> On Wed, Apr 5, 2017 at 1:35 AM, Sankalp Bagaria <sankalp@cdac.in> wrote:
>
>> Hello,
>>
>> How is Certificate Compression advantageous over tls cached-info
>> extension?
>> Only case I can think of is - when the certificate is being sent for the
>> first time,
>> it can be compressed. Since the client doesn't have a copy of the
>> certificate,
>> cached-info can't be used. Are there more cases where compression is
>> useful?
>>
>
> Does cached-info not represent a privacy info-leak by disclosing past
> sessions prior to authenticating the new session? Versus compression, which
> limits it to the session and thus reveals no new/additional information.
> That was certainly true for TLS1.2
>

This will also be true in TLS 1.3, even with encrypted certificates because
(hopefully) they
will be a lot smaller. Though you could of course pad out to the same size
:)

-Ekr