linux-kernel - Re: [PATCH 1/3] crypto: authenc

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Message-ID: <AM4PR0401MB1876509BEA44E70B77BA3BAAE7B30@AM4PR0401MB1876.eurprd04.prod.outlook.com>
Date:	Wed, 9 Mar 2016 08:18:12 +0000
From:	Cristian Stoica <cristian.stoica@....com>
To:	Tadeusz Struk <tadeusz.struk@...el.com>,
	"herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>
CC:	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH 1/3] crypto: authenc - add TLS type encryption

Hi Tadeusz,

>> SSL/TLS is prone to this implementation issue and many user-space libraries got this wrong. It would be good to see >>some numbers to back-up the claim of timing differences as not being an issue for this one.

>It is hard to get the implementation right when the protocol design is error prone.
>Later we should run some tests on it and see how relevant will this be for a remote timing attack.

Why later and who will do it?

If it's only a proof of concept, then it's a bad idea. You are practically advertising a use-it-but-cross-your-fingers implementation.
If you intend to submit another hardware driver which _is_ constant time, then it is even more a bad idea. The end-user doesn't know which driver is actually running and if it is resistant or not to timing attacks.

Cristian S.