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To: Ramus who wrote (24608)	3/22/1999 9:21:00 AM
From: Clarksterh	Read Replies (3) \| Respond to of 152472

Walt - Also, if you look at a system diagram(either forward or reverse link) the long code is applied then the Walsh cover, then the spreading codes(partial transmitter forward/reverse). The point of all this is that the channels are separated by Walsh codes. I am reasonably sure that the Walsh codes are not used to separate channels on the reverse link. Instead they are used to code the data stream and a mobile will use most of the different Walsh codes in any one second (thus it cannot be used to separate the various mobiles). The reason that the Walsh codes are not used as channels on the reverse link is that the Walsh codes do not 'work' when not time synched with each other and this is difficult to control on the reverse link. Just FYI. Whew! Now, having said all that..... you're right in your assumption that if we know the various codes and PN sequences we should be able to decode the data. But as Leland pointed out... it looks like we could be using essentially a public key encryption system in IS-95 CDMA. I have the feeling that it is very very secure. I now agree that it is pretty secure in real time, but I am somewhat more doubtful about non-realtime security since 42 bit 'encryption' is not that secure. Again, I'll have to do some more research. Clark PS I also discovered why I thought that the long code was not used on the forward channel - it is not used for spreading or channel separation, but is essentially used just for data scrambling (i.e. at a very low rate). I was looking in the wrong part of the spec. PPS For those still interested in Cinecomm and CDMA: Does my f**kup change the info about whether Cinecomm is tied to CDMA? No, in my opinion, (FWIW!) there is no particular reason why Cinecomm should be tied to CDMA. There are plenty of good encryption techniques which do not require CDMA, and the data security of CDMAOne is, in a sense, incidental to its more important characteristic of being interference resistant.