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Re: [TLS] Enforcing keyUsage restrictions (was Re: Safe ECC usage)

Manuel Pégourié-Gonnard <mpg@elzevir.fr> Sat, 12 October 2013 03:23 UTC

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Date: Sat, 12 Oct 2013 05:22:19 +0200
From: Manuel Pégourié-Gonnard <mpg@elzevir.fr>
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To: Santosh Chokhani <SChokhani@cygnacom.com>, Brian Smith <brian@briansmith.org>, Peter Gutmann <pgut001@cs.auckland.ac.nz>
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Subject: Re: [TLS] Enforcing keyUsage restrictions (was Re: Safe ECC usage)
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On 12/10/2013 03:15, Santosh Chokhani wrote:
> DS bit for RSA based TLS server is not appropriate since the Server key is
> used by the client to encrypt and never used for digital signature
> verification.
> 
Your seem to have RSA key exchange in mind, while Brian was talking about
ECDHE_RSA or DHE_RSA key exchanges, where the server's RSA key is used to sign
the parameters in the ServerKeyExchange message. The point was precisely that,
if the keyUsage bits were respected, then setting only DS would force to use
only forward secret key exchanges with this certificate.

Manuel.

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