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To: Clarksterh who wrote (24589)	3/21/1999 10:04:00 PM
From: Ramus	Read Replies (2) \| Respond to of 152472

Clark, All, Please forgive my imprecision here but CDMA security is basically as follows: for each mobile phone there is a long code mask(public) and long code mask (private). The long code itself is a PN sequence generator polynomial of length 2^42-1 bits. The mask is a sequence of 42 bits that are XOR'd with this PN sequence creating a new sequence. I could not find information on how the code masks are produced(which makes sense!!). When a call is being established between a mobile and basestation the mask to be used is specified by the mobile and it is then used on the forward and reverse links. Also, according to my worn copy of the EIA/TIA/IS-95 specification there is a randomization seeded to these long codes that occurs, generated by the mobile, during the initial negotiation between the mobile and the basestation. It would appear that a mobile station can select between two levels of security when negotiating a call and this is related to the selection of the public or private long code masks. BTW, I'm not suggesting this is a user selectable feature!! Sorry I couldn't be more precise. The EIA/TIA/IS-95 specification is not very detailed in it's explanations of what goes on with security in these systems. I believe this is because a degree of flexibility was built in to allow various networks to customize their security features and make them unique. And also of course to allow things to be secret!! Walt