To: Keith Feral who wrote (20115 ) 3/8/2002 1:50:12 PM From: Eric L Read Replies (1) | Respond to of 196656 Keith, << Isn't this what the SIM/RUIM is designed to do in the dual mode handsets? >> Not really. The CDMA RUIM is a smart card that is essentially a computer without its own display or input mechanism contained on a single piece of highly tamper resistant silicon beneath a contact plate (for I/O) encased in a piece of plastic that is easily removable from the phone. The architecture of that single piece of silicon is: * a 16-bit or 32-bit-CPU * ROM for an OS (and some elementary applications and stored algorithms) * Some EEPROM or Flash for data storage - files including executables -> Applications -> Browsers -> Bookmarks -> Algorithms -> Keys (public and/or private) -> Certificates -> Lists (speed dial, bookmarks, preferred networks, etc) -> Parameters -> Subscribed services -> Stored messages (SMS/EMS/MMS) -> Etc. * Some RAM for computation of algorithms or other math * a bus to connect it all together * contacts for I/O The primary thing that the RUIM is doing in a mixed CDMA GSM environment is authenticate to a GSM network (no SIM or RUIM, no authentication in GSMland). Network authentication in GSMland is a shared private key scheme. Algorithms are stored in the RUIM OS or rewritable EEPROM and processed or computed in the RUIM RAM, and transmitted to the network through the terminal and capable of receiving a network response. Much (all) of the functionality I described here could be done (can still be done) on soldered in chips on the handset - and for many years Qualcomm attempted to make the point that this was preferable, and in fact this was one of Qualcomm's "5 principles". Despite this, in GSMland today as always (2G/2.5G/3G) authentication to a GSM network must take place using a SIM, USIM, or Removable User Identity Module (RUIM). At the risk of repetition, and although it has other functionality, all that the RUIM is doing from a GSM CDMA interoperability point of view is enabling authentication to a GSM network, and that authentication is frequency independent and the capability is portable between phones or devices. - Eric -