[147964] in cryptography@c2.net mail archive
Re: [Cryptography] What's a Plausible Attack On Random Number
daemon@ATHENA.MIT.EDU (Yaron Sheffer)
Sat Nov 2 12:25:10 2013
X-Original-To: cryptography@metzdowd.com
Date: Sat, 02 Nov 2013 12:50:06 +0200
From: Yaron Sheffer <yaronf.ietf@gmail.com>
To: John Denker <jsd@av8n.com>, John Gilmore <gnu@toad.com>,
Jerry Leichter <leichter@lrw.com>,
"cryptography@metzdowd.com List" <cryptography@metzdowd.com>
In-Reply-To: <527412D2.7050707@av8n.com>
Cc: David Mercer <radix42@gmail.com>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
On 2013-11-01 22:45, John Denker wrote:
> On 11/01/2013 04:04 AM, Yaron Sheffer wrote:
>> It sounds like a quick addition to DHCP - an extension that gets you
>> 256 bits from the server, would solve 99% of the problem we have with
>> embedded devices. It will not be sufficient for high-security
>> environments, because an attacker might be listening on the local
>> LAN, but it will provide the entropy we need to initialize SSH, TLS,
>> IPsec. And it is much better than relying on fixed information (MAC
>> address etc.) and a few bits of timing.
>>
>> Looks very much like an "implement it, standardize it and forget it"
>> kind of thing to me.
>
> Alas, that leaves important parts of the problem unsolved. We
> cannot "forget it" until we solve the whole problem.
>
> For example: SSH has to cut host keys when it is first used
> (if not before). This requires a lot of high-quality randomly-
> distributed bits. There are a gazillion scenarios where this
> has to happen /before/ the first DHCP happens. For example,
> I might need to "ssh root@localhost" in order to configure DHCP.
>
I'm probably missing something obvious, but why is "ssh localhost" part
of your standard routine? I've never had to use it, I can always either
use "sudo" or simply login as root from a console.
Also, desktop distros are often preconfigured with DHCP. For servers,
even if you don't take your IP from DHCP, you can request other
parameters (and my hypothetical random extension) with a DHCPINFORM message.
Thanks,
Yaron
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