H.235 & Implementors Guide

[Orit Levin]

Jim!

Just before the closure of Implementors Guide regarding the

4.2 EP-GK Authentication (Non-Subscription Based)

Is our understanding of the XOR'ing algorithm right?

See below:
1. Take the GK Id (GKID) as a sequence of BMP characters (each 16 bit long) of length N.
2. Take the 16 bit long Random value (RND) N times to build the string of the same length as GKID above.
3. Take the 16 bit long requestSeqNum (SQN) N times to build the string of the same length as GKID above.
4. XOR bitwise three of these same length bit strings.

GKID             !BMP1 !BMP2 !BMP3 !BMP4 !BMP5   !
XOR
RND 16 bit   !RND16!RND16!RND16!RND16 !RND16!  
XOR
SQN 16 bit   !SQN16!SQN16!SQN16!SQN16!SQN16!  


May be it would be useful to put such an explanation into the Implementors Guide?

Orit Levin
RADVision Inc.,
575 Corporate Drive - Suite 420
Mahwah, NJ 07430
Tel:    201-529-4300 (230)
Fax:   201-529-3516
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