Subject: [Sip] GRUU issue 3: big gruu's

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 12 May 2004 02:41:28 -0400

Currently, the spec suggests an algorithm for using AES encryption to 
generate a GRUU algorithmically, and to store the mapping from the gruu 
to the instance iD/AOR within the encrypted GRUU. This works, but 
results in really long GRUUs - 129 characters, in fact. This was seen as 
an issue for wireless. I'll note that, with a stateful sigcomp 
implementation, it would be compressed out after being sent once, since 
it won't change for a particular UA.

Note that this algorithm for computing the gruu is nor mandatory - its 
an implementation suggestion. However, given the large gruus is 
produces, do people have heartburn with the mechanism? If so, does 
anyone have a better idea?

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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From: "Christian Stredicke" <[email-masked]>
Date: Wed, 12 May 2004 09:37:06 +0200

Of course, you can always take only a piece of the encrypted string and code
it more efficiently than with hex numbers. These encryption algorithms
should generate evenly distributed probabilities across all bits so that
this approach is valid, even if it reduces the security.

I personally think that a 20-character string like "3Hf4hJji04fh6yDfd3"
which gives roughly 120 bits of security should practically be pretty much
ok.

CS

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of Jonathan
> Rosenberg
> Sent: Wednesday, May 12, 2004 8:41 AM
> To: [email-masked]
> Subject: [Sip] GRUU issue 3: big gruu's
>