Re: ssh, /dev/urandom

[Philip Charles <philipc@copyleft.co.nz>]

On Tue, 17 Dec 2002, Hubert Chan wrote:

> Philip> 2.  Does ssh only use urandom once, that is to generate keys while it is
> Philip> configuring?  Again I have assumed yes.
>
> I don't think the public/private key (i.e. host key) generation is much
> of an issue, since one should be able to generate these on a different
> machine with a good random number source, and copy them over.
>
> But ssh needs to generate a session key.  Since public key crypto is
> slower than symmetric crypto, ssh only uses the host key to send a
> session key, which is used to do symmetric crypto.  I don't know the
> *exact* details, but that's the general idea, and it's used in pretty
> much all public key crypto systems, or at least in the ones made by
> people who know what they're doing.

Thanks.  Helpful.

Phil.

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