questions on RFC2631 and DH key agreement

[Joseph Ashwood]

----- Original Message ----- 
From: "' =JeffH '" <Jeff.Hodges at KingsMountain.com>
To: <cryptography at metzdowd.com>
Cc: "' =JeffH '" <Jeff.Hodges at KingsMountain.com>
Sent: Friday, February 01, 2008 1:53 PM
Subject: questions on RFC2631 and DH key agreement


> (ya and yb) if { p, q, g, j } are known to both parties.

> So if p, q, g are not static, then a simplistic, nominally valid, DH 
> profile
> would be to..
>      a                                         b
>  ----------                               ----------
>  g, p, ya ------------------------------------>
>      <--------------------------------------- yb
> ..yes?

I would actually recommend sending all the public data. This does not take 
significant additional space and allows more verification to be performed. I 
would also suggest looking at what exactly the goal is. As written this 
provides no authentication just privacy, and if b uses the same private key 
to generate multiple yb the value of b will slowly leak.

> Other than for b perhaps wanting to verify the correctness of { p, q, g, 
> j }
> ("group parameter validation"), is there any reason to send q ?

You can then use the gpb trio for DSA, leveraging the key set for more 
capabilities.
                Joe 

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