Tutorial[11] - LTE security

LTE security is an issue that is of paramount importance. It is necessary to ensure that LTE security measures provide the level of security required without impacting the user as this could drive users away.

Nevertheless with the level of sophistication of security attacks growing, it is necessary to ensure that LTE security allows users to operate freely and without fear of attack from hackers. Additionally the network must also be organised in such a way that it is secure against a variety of attacks.

LTE security basics

When developing the LTE security elements there were several main requirements that were borne in mind:

• LTE security hand to provide at least the same level of security that was provided by 3G services.
• The LTE security measures should not affect user convenience.
• The LTE security measures taken should provide defence from attacks from the Internet.
• The secruity functions provided by LTE should not affect the transition from existing 3G services to LTE.
• The USIM currently used for 3G services should still be used.

To ensure these requirements for LTE security are met, it has been necessary to add further measures into all areas of the system from the UE through to the core network.

The main changes that have been required to implement the required level of LTE security are summarized below:

• A new hierarchical key system has been introduced in which keys can be changed for different purposes.
• The LTE security functions for the Non-Access Stratum, NAS, and Access Stratum, AS have been separated. The NAS functions are those functions for which the processing is accomplished between the core network and the mobile terminal or UE. The AS functions encompass the communications between the network edge, i.e., the Evolved Node B, eNB and the UE.
• The concept of forward security has been introduced for LTE security.
• LTE security functions have been introduced between the existing 3G network and the LTE network.

LTE USIM

One of the key elements within the security of GSM, UMTS and now LTE was the concept of the subscriber identity module, SIM. This card carried the identity of the subscriber in an encrypted fashion and this could allow the subscriber to keep their identity while transferring or upgrading phones.

With the transition from 2G - GSM to 3G - UMTS, the idea of the SIM was upgraded and a USIM - UMTS Subscriber Identity Module, was used. This gave more functionality, had a larger memory, etc.

For LTE, only the USIM may be used - the older SIM cards are not compatible and may not be used.