Post on 04-Jan-2016
1
Using GSM/UMTS forSingle Sign-On
28th October 2003SympoTIC 2003
Andreas Pashalidis and Chris J. Mitchell
2
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
3
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
4
Why do we need SSO ?Current Situation:
Network users interact with multiple service providers.
5
Why do we need SSO ?Problems:
Usability, security, privacy…
6
What is SSO ?
A mechanism that allows users to authenticate themselves to
multiple service providers, using only one identity.
7
SSO – How ?Establish trust relationships, common security
infrastructure (e.g. PKI), sign contractual agreements…
8
SSO – some examples Kerberos
TTP = Kerberos server 1) Authenticates user (password), issues “ticket”. 2) User shows ticket to service provider.
Microsoft Passport TTP = www.passport.com 1) Authenticates user (password), installs encrypted cookie. 2) Service Provider reads the cookie.
Liberty Alliance TTP = “Identity Provider” 1) Authenticates user, issues “assertion” (XML). 2) Assertion is shown to service provider.
9
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
10
Review of GSM Security
11
Review of GSM Security
12
Review of GSM Security
13
Review of GSM Security
14
Review of GSM Security
15
Review of GSM Security
16
Review of GSM Security
17
Review of GSM Security
18
Review of GSM Security
19
Review of GSM Security
Encrypted under Kc
If the visited network can decrypt, then the SIM is authentic (IMSI matches Ki)
20
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
21
Architecture - before
22
Architecture – after (1)
23
Architecture – after (2)
24
Architecture
25
Architecture
Service providers form trust relationships with the home
network.
26
Architecture
Singe Sign-On using SIM (IMSI) !
27
SSO Protocol
28
SSO Protocol
29
SSO Protocol
30
SSO Protocol
31
SSO Protocol
32
SSO Protocol
33
SSO Protocol
34
SSO Protocol
35
SSO Protocol
36
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
37
Replay Attack
Attacker could capture this
message and replay it later in
order to impersonate the user identified
by the IMSI.
38
Replay Attack
At the time of replay another
RAND will be selected by the service provider and the protocol
will fail.
fresh !
old ! X
39
Reflection Attack
The service provider SP “A” is malicious.
It wants to impersonate the user to SP “B”.
40
Reflection Attack
41
Reflection Attack
42
Reflection Attack
43
Reflection Attack
44
Reflection Attack
45
Reflection Attack
46
Reflection Attack
X
47
Other AttacksSIM theft / cloning SIM PIN is optional! Need two-factor user authentication.
Home network server is SPoF Vulnerable to DoS attack. It is assumed that it is well-protected.
Attacks on the SP-home network link Link must be integrity-protected and encrypted. SSL/TLS, VPN, IPSec, etc…
48
Agenda
Introduction to SSO. Review of GSM security. How to SSO using GSM. Some Attacks. Conclusions.
49
Advantages
50
Disadvantages
51
Extension for UMTS
52
Thanks!Questions?