GSM Security Feature, Threats and Solution

The GSM logo 

Background Information

GSM stands for Global System for Mobile Communications. It is a standard used to describe technologies for second generation or 2G networks. Using the words we learned from school, this GSM is a circuit switched network and is mainly used for full duplex voice telephony.

Technology Used In GSM

1. Gaussian Minimum Shift Keying (MGSK)
2. Phase Shift Keying (PSK)
3. Time Division Multiple Access (TDMA)
4. Frequency Division Duplex (FDD)

Security Feature

GSM has only a moderate level of service security. It was being designed in a way that it had to authenticate the subscriber with the use of a pre-shared key. It also has a challenge-response. The link between the subscriber and the base station can be encrypted. On the whole, GSM offers confidentiality and authentication, but with limited authorization capabilities.

Cryptographic algorithms are used for security purposes in GSM. For ensuring over-the-air voice privacy, the A5/1 and A5/2 stream ciphers are used.

Threats

The A5/2 is weaker and therefore is easier to find loopholes in it. It can be broken with a ciphertext-only attack. Though the A5/1 is stronger, it also can be broken with a rainbow table attack. 

Solution

GSM uses USIM (Subscriber Identity Module) to prevent connections to fake base stations and downgrade attacks. Users will be protected in the medium term.

References

http://www.gsmfordummies.com/

http://www.gsmworld.com/

http://www.etsi.org/WebSite/Technologies/gsm.aspx