Re: [TLS] [Cfrg] 3DES diediedie

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 08 September 2016 05:53 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Richard Hartmann <richih.mailinglist@gmail.com>
Thread-Topic: [TLS] [Cfrg] 3DES diediedie
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Date: Thu, 8 Sep 2016 05:53:29 +0000
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Subject: Re: [TLS] [Cfrg] 3DES diediedie
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Richard Hartmann <richih.mailinglist@gmail.com> writes:

>Is it correct when I say that the embedded programmers you talked to don't 
>care about any form of DES as they need/must/prefer to do AES, anyway?

The only data point I have is that every time I've tried to disable DES in
a new release (and by DES I mean single DES, not 3DES) I've had a chorus of 
complaints about it vanishing.  Unfortunately I don't have anything more
than that, you only find out about things like this when they break stuff.
Certainly DES still sees a surprising amount of use, and in many cases it's
quite justified, whatever you're protecting is adequately safeguarded with
DES.  For example burglar alarms, if they use real encryption (far too many
use "encryption" that would more accurately be described as data masking),
often use DES, no doubt based on Microchip App Note 583 or freely available
source like despiccable, which runs in 20 bytes of RAM (if your burglar alarm
is advertised as having a "RISC based CPU" then it's probably using a PIC,
having a processor so spartan it can barely add is now a marketing feature if
you use the right name for it).  They'll be using DES forever, because the 
entire environment they operate in runs DES.

>If yes, there's no reason in the embedded world that would prevent a 
>diediedie.

See above.  You're not going to get rid of DES.  And, as I've pointed out
earlier, the embedded world won't even know your diediedie exists, and if
it's pointed out to them they'll ignore it.  Alarms, for example, send data
quantities measured in bytes, so some academic attack that would take 500 
million years to acquire the necessary data isn't going to lose anyone any 
sleep.  It's a nice piece of work, but you need to look at what practical 
effect it has on real, deployed systems...

Peter.