[Cryptography] What's a Plausible Attack On Random Number Generation?

[John Denker]

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 at 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.