Re: [TLS] Is it possible for a client to offer TLS 1.3, but not be forced to support RSA PSS in TLS 1.2?

Martin Thomson <martin.thomson@gmail.com> Wed, 30 May 2018 01:17 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Wed, 30 May 2018 11:17:21 +1000
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To: Andrey Jivsov <crypto@brainhub.org>
Cc: David Benjamin <davidben@chromium.org>, "<tls@ietf.org>" <tls@ietf.org>
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Subject: Re: [TLS] Is it possible for a client to offer TLS 1.3, but not be forced to support RSA PSS in TLS 1.2?
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On Wed, May 30, 2018 at 7:20 AM Andrey Jivsov <crypto@brainhub.org>; wrote:
> The issue here is that some hardware devices don't implement RSA CRT
> method with PSS, because they hard-wide RSA, legacy padding, and CRT
> method in one operation. RSA PSS can still be done, but only via a
> general modexp operation, which will be ~2x shower. Therefore, in these
> scenarios PSS incurs 2x performance penalty.

I'm fairly certain that we've had this discussion before.  What is new?