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Message-ID: <20151023145631.GA21048@gremlin.ru>
Date: Fri, 23 Oct 2015 17:56:31 +0300
From: gremlin@...mlin.ru
To: oss-security@...ts.openwall.com
Subject: Re: Prime example of a can of worms
On 2015-10-21 22:27:33 -0600, Kurt Seifried wrote:
> I can't even begin to think how slow this would be on hardware
> limited systems like $20 routers and whatnot (in theory you could
> have systems taking tens of minutes), which would not be popular
> with consumers (turn the unit on and wait from 0 seconds to an
> hour or so for the web interface to come up!).
Normally, all those $20 (or even $10) routers don't need to generate
keys at the first start - they are configured via plain HTTP given
that user's PC is connected to a "LAN" port with a cable. And only
when user activates the outside access (via VPN or SSH) the keys are
to be generated - possibly in several hours, like those 17 hours the
`openssh dhparam -5 8192` command took at my notebook :-)
> With this data in mind I think we need to generally encourage
> everyone to go to a minimum of 2048 bit primes
For my clients, I force the use of 4096 bit for over 5 years.
> (which should last a few more years assuming quantum computers
> don't suddenly make factorization easy)
That wouldn't be suddenly. At least I'm not going to worry until
they would be able to factorize some number close to 2^160 - say,
266508845991748914569771929356540352347893240569. And yes, I know
one divisor: it is 4458192223320340849 :-)
> and establish some safe methods of creating them, much like
> generating CA encryption keys we need to ensure the systems/
> software in use are correct, the entropy is available (and
> not manipulated) and so on.
Here we come to trusted execution, trusted computation and so on.
> Ideally we'd like to see people using different primes (e.g.
> hardware manufacturers not using the same primes as everyone
> else) and where possible people needing more security (e.g. a
> VPN hosting provider) should generate their own keys securely.
Theory is fine. But in practice we see weakened algorithms with
(intentionally?) reduced key size.
--
Alexey V. Vissarionov aka Gremlin from Kremlin <gremlin ПРИ gremlin ТЧК ru>
GPG: 8832FE9FA791F7968AC96E4E909DAC45EF3B1FA8 @ hkp://keys.gnupg.net
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