Re: [Cfrg] Question about RSA keys
Hanno Böck <hanno@hboeck.de> Sat, 19 November 2016 09:07 UTC
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Date: Sat, 19 Nov 2016 10:06:59 +0100
From: Hanno Böck <hanno@hboeck.de>
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Subject: Re: [Cfrg] Question about RSA keys
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On Sat, 19 Nov 2016 10:48:18 +0200 Yoav Nir <ynir.ietf@gmail.com> wrote: > However, most servers (and clients) in the foreseeable future are > going to support both TLS 1.2 and TLS 1.3, and they’re going to do > this with a single certificate that might have an RSA key. > > So my question is, is there a problem with having the server (or > client) signing some TLS transcripts with PKCS#1 and others with > RSA-PSS? This came up before. Ideally you'd want key separation, but this is complicated. There are to my knowledge no known attacks that exploit the combination of PKCS #1 1.5 and PSS. However we've been using the same keys for PKCS #1 1.5 encryption and signatures for ages and this is most likely more concerning, see [1] and DROWN [2]. I think the theoretical concerns about mixing PKCS #1 1.5 and PSS with the same key are minor compared to the issues raised by combining encryption and signatures with the same key. [1] http://euklid.org/pdf/CCS15.pdf [2] https://drownattack.com/drown-attack-paper.pdf -- Hanno Böck https://hboeck.de/ mail/jabber: hanno@hboeck.de GPG: FE73757FA60E4E21B937579FA5880072BBB51E42
- [Cfrg] Question about RSA keys Yoav Nir
- Re: [Cfrg] Question about RSA keys Hanno Böck
- Re: [Cfrg] Question about RSA keys Yoav Nir