Re: [TLS] Using RSA PSS in TLS

Johannes Merkle <johannes.merkle@secunet.com> Mon, 14 October 2013 12:19 UTC

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Date: Mon, 14 Oct 2013 14:19:42 +0200
From: Johannes Merkle <johannes.merkle@secunet.com>
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To: Santosh Chokhani <SChokhani@cygnacom.com>, "<tls@ietf.org>" <tls@ietf.org>
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Subject: Re: [TLS] Using RSA PSS in TLS
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Santosh Chokhani schrieb am 14.10.2013 13:19:
> Oops.  My bad.  I mixed up signature algorithms with SPKI.

If the certificate contains id-RSASSA-PSS (RFC 4055) in SubjectPublicKeyInfo, the client could tell, but there are
several issues with that approach:
- The use of id-RSASSA-PSS is optional
- The specification of the PSS-parameters in id-RSASSA-PSS is optional (RFC 5756)
- Most implementations don't support id-RSASSA-PSS (see http://rsapss.hboeck.de/rsapss-1.0.2.pdf)

As far as I understand RFC 5246, the Server Key Exchange message specifies the signature algorithm only by the enum {
dhe_dss, dhe_rsa, dh_anon, rsa, dh_dss, dh_rsa, ...}.

Johannes

-- 
Johannes