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Tuesday, April 1, 2014
Friday, March 21, 2014
Whenever GSM mobile equipment (ME) is switched on, it has to be registered with operator’s network. For this registration, operator network should identify the user. There is a well-defined authentication procedure for verifying user identity of ME. The procedure is as follows.
- A GSM ME is switched ON.
- ME uses a common channel to communicate with the operator network by providing IMSI.
- When operator network detects an active unregistered ME, it verifies its IMSI. If it is a valid one, authentication procedure starts. Operator network will then fetch Ki corresponding to IMSI received from its database and will generate a random number (RAND). RAND is then encrypted with A3 algorithm with Ki as key to produce an output called SRES_1. Along with this, operator network will send this RAND to ME along with an indication of the algorithm used to generate SRES_1.
- When ME receives RAND, it will pass this to SIM card along with the command RUN GSM ALGORITM. SIM card will encrypt this RAND with the same algorithm used by network operator using Ki in the SIM card as key and will generate SRES_2 as output. ME will send SRES_2 back to operator network.
- On receiving SRES_2, operator network will match it with SRES_1 generated by it. If both matches authentication is success and ME is granted access to operator network
It is important to note that during authentication procedure, Ki is never transmitted anywhere. It always resides in operator network’s data base and in SIM card. Thus there is no way to get Ki for a third party.
Next Part - GSM Authentication Procedure
Wednesday, March 19, 2014
MSISDN - Mobile Station International Subscriber Directory Number. (Normal mobile number which we use)
PLMN - Public land mobile network
PIN/CHV - Personal identification number or Card Holder Verification information
PUK - PIN Unblocking Key
MNC/MCC - Mobile Country code/Mobile network code
ESN - Electronic Serial number
MEID - Mobile equipment Identifier
UIM - User Identity Module
RUIM - Removable User Identity Module
RUIMID - 32 bit electronic identification number ID unique to the RUIM
MIN - Mobile Identification Number: A 10-digit number assigned by a wireless operator to a Mobile station.
Next part - SIM card Security Features
Monday, March 17, 2014
Saturday, March 15, 2014