GSM SECURITY AND ENCRYPTION

What is GSM? GSM stands for Global System for Mobile communication The GSM emerged in the early 1970’s The GSM is a circuit switched system that divides each 200KHZ channel into eight 25KHZ timeslots The GSM owns a market share of more than 70 % of the digital cellulor subscribers.

Why GSM? International roaming Low-cost mobile sets and base stations High quality speech Compatability with integrated services digital network(ISDN) and other telephone company services Support for new services.

GSM Brief history 1982 CEPT establishes a GSM group inorder to develop the standerds for a pan european cellulor mobile system 1987 Time Division Multiple Access (TDMA) is choosen as the access method 1988 GSM system is validated

GSM-Architecture

GSM-User services Telephony services Data services Supplementary services

GSM security model The purpose of GSM security: The access to the mobile services. Any relavent item from being disclosed at the radio path,mainly inorder to ensure that. Privacy of user- related information.

Security features of GSM Authentication of registered subscribers only. Secure data transfer through the use of encryption. Subscriber identity protection. Mobile phones are inoperable without a SIM. Duplicate SIM or not allowed in the network.

The Authentication Procedure The mobile station send IMSI to the network. The network received IMSI and found corresponding KI of that IMSI. The network generated a 128 bit random number(RAND) and sent it to the mobile station over the air interface. The MS calculates a SRES with A3 algorithm using the given challenge(RAND) and KI residing in the SIM.At the same time networks calculates the SERS using the same algorithm and same inputs The MS sends SERS to the network The network test the SERS for the validity

Authentication process

Encryption of the data Encrypted communication is initiated by a ciphering mode request command for the GSM network A5 algorithm used for encrypt the data The MS authentication is an optional procedure in the beginning of the call,but it is usually not performed

Base Station Subsystem Encryption process Mobile Stations Base Station Subsystem Network Management BTS OMC Exchange System BTS VLR MSC BSC HLR AUC BTS EIR

Other security features Subscribers identity protection Smart card

Overview of cryptography Symmetric algorithms Block ciphers Stream ciphers

A3 – MS Authentication Algorithm Goal Generation of SRES response to MSC’s random challenge RAND

Applications 1. Mobile telephony 2. GSM-R 3. Telemetry system -fleet management -automatic meter reading -toll collection 4.Value added services

FUTURE SCOPE The range of applications offered, with home banking and electronic trading emerging. The development of interworking between different wireless networks with different cellular technologies, cordless and GSM, and satellite and GSM The development of advanced new broadband wireless technology offering at least 144Kbit/s transmission rates by 2000. The development of new types of terminals with data only facilities over GSM on offer without the need for a cellular phone.

Conclusion The security mechanisms specified in the GSM standard make it the most secure cellular telecommunications system available. The use of authentication, encryption, and temporary identification numbers ensures the privacy and anonymity of the system's users, as well as safeguarding the system against fraudulent use. Even GSM systems with the A5/2 encryption algorithm, or even with no encryption are inherently more secure than analog systems due to their use of speech coding, digital modulation, and TDMA channel access

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