[147949] in cryptography@c2.net mail archive
Re: [Cryptography] What's a Plausible Attack On Random Number
daemon@ATHENA.MIT.EDU (John Denker)
Fri Nov 1 19:00:54 2013
X-Original-To: cryptography@metzdowd.com
Date: Fri, 01 Nov 2013 13:45:06 -0700
From: John Denker <jsd@av8n.com>
To: Yaron Sheffer <yaronf.ietf@gmail.com>, John Gilmore <gnu@toad.com>,
Jerry Leichter <leichter@lrw.com>,
"cryptography@metzdowd.com List" <cryptography@metzdowd.com>
In-Reply-To: <52738ACD.6030502@gmail.com>
Cc: David Mercer <radix42@gmail.com>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
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.
Rather than writing repetitious email, I put together a little
document on the care and feeding of a secure PRNG, including
proper provisioning:
http://www.av8n.com/computer/htm/secure-prng.htm
This is a first draft. It is a work in progress. Comments and
suggestions are welcome.
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