26-05-2012, 05:38 PM
Security Issues in Mobile Communication Systems
[attachment=23238]
What is different about wireless networks?
Low bandwidth
minimize message sizes, number of messages
Increased risk of eavesdropping
use link-level encryption ("wired equivalency")
Also wireless networks typically imply user/device mobility
Security issues related to mobility
authentication
charging
privacy
Focus of this presentation
GSM/GPRS security
Authentication
one-way authentication based on long-term shared key between user's SIM card and the home network
Charging
network operator is trusted to charge correctly; based on user authentication
Privacy
data
link-level encryption over the air; no protection in the core network
identity/location/movements, unlinkability
use of temporary identifiers (TMSI) reduce the ability of an eavedropper to track movements within a PLMN
but network can ask the mobile to send its real identity (IMSI): on synchronization failure, on database failure, or on entering a new PLMN
network can also page for mobiles using IMSI
3GPP/UMTS enhancements (current status)
Authentication
support for mutual authentication
Charging
same as in GSM
Privacy
data
some support for securing core network signaling data
increased key sizes
identity/location/movements, unlinkability
enhanced user identity confidentiality using "group keys"
a group key is shared by a group of users
Other improvements
integrity of signaling, cryptographic algorithms made public
What is different in the wireless Internet?
Potentially low cost of entry for ISPs supporting mobile access
Consequently, old trust assumptions as in cellular networks may not hold here
between user and home ISP
between user and visited ISP
between ISPs
Implications: potential need for
incontestable charging
increased level of privacy
Relevant even in cellular networks?
[attachment=23238]
What is different about wireless networks?
Low bandwidth
minimize message sizes, number of messages
Increased risk of eavesdropping
use link-level encryption ("wired equivalency")
Also wireless networks typically imply user/device mobility
Security issues related to mobility
authentication
charging
privacy
Focus of this presentation
GSM/GPRS security
Authentication
one-way authentication based on long-term shared key between user's SIM card and the home network
Charging
network operator is trusted to charge correctly; based on user authentication
Privacy
data
link-level encryption over the air; no protection in the core network
identity/location/movements, unlinkability
use of temporary identifiers (TMSI) reduce the ability of an eavedropper to track movements within a PLMN
but network can ask the mobile to send its real identity (IMSI): on synchronization failure, on database failure, or on entering a new PLMN
network can also page for mobiles using IMSI
3GPP/UMTS enhancements (current status)
Authentication
support for mutual authentication
Charging
same as in GSM
Privacy
data
some support for securing core network signaling data
increased key sizes
identity/location/movements, unlinkability
enhanced user identity confidentiality using "group keys"
a group key is shared by a group of users
Other improvements
integrity of signaling, cryptographic algorithms made public
What is different in the wireless Internet?
Potentially low cost of entry for ISPs supporting mobile access
Consequently, old trust assumptions as in cellular networks may not hold here
between user and home ISP
between user and visited ISP
between ISPs
Implications: potential need for
incontestable charging
increased level of privacy
Relevant even in cellular networks?