Re: [TLS] Using RSA PSS in TLS

Johannes Merkle <johannes.merkle@secunet.com> Mon, 14 October 2013 09:33 UTC

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Date: Mon, 14 Oct 2013 11:29:22 +0200
From: Johannes Merkle <johannes.merkle@secunet.com>
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Subject: Re: [TLS] Using RSA PSS in TLS
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Johannes Merkle schrieb am 14.10.2013 10:39:
> While the current discussion on this list is about ECC, I would like to raise the question if it were not desirable to
> allow usage of provably secure RSA-PSS signatures from PKCS#1v2.1 in TLS.
> 
> Of course, an issue with this idea is that, if we replace DHE_RSA and ECDHE_RSA with DHE_PSS and ECDHE_PSS, we end up
> with a whole bunch of new cipher suites. An alternative could be a new extension signaling the RSA version used (with
> PKCS#1v1.5 as default).
> 

I forgot to mention that PSS introduces additional parameters. RFC 4055 defines
RSASSA-PSS-params  ::=  SEQUENCE  {
         hashAlgorithm      [0] HashAlgorithm DEFAULT
                                   sha1Identifier,
         maskGenAlgorithm   [1] MaskGenAlgorithm DEFAULT
                                   mgf1SHA1Identifier,
         saltLength         [2] INTEGER DEFAULT 20,
         trailerField       [3] INTEGER DEFAULT 1  }

This added flexibility is an even stronger argument for a new extension.

-- 
Johannes