SA Access Control Security Violations; OSI Security Architecture; Network Security Model Security Violations.

OSI

1. Chapter 1 -
Introduction
•Security Violations
•OSI Security Architecture
•Network Security Model

2. Security Violations
File F is SENSITIVE
F
A -------> B
C CAPTURESF
1. Capture

3. Security Violations
Authorisation File F is SENSITIVE
A sends message toB: ”Update F with names”
A(m) m B(F)
C INTERCEPTSm and adds name of C
A(m) mC(m) mB(F)
2. Intercept -Update

4. Security Violations
Authorisation File F is SENSITIVE
C PRETENDSto be A
C sends message toB: ”Update F with name of C”
{C}A(m) m B(F)
3. Substitute

5. Security Violations
A sends message to B: ”STOPC’s r/w access”
A(m0) m0 B(m1)
B(m1) m1 STOP(C)
C INTERCEPTSm0:
A(m0) m0C m0B(m1)
C(r/w ACCESS)
B(m1) m1 STOP(C)
4. Intercept -Preempt

6. Security Violations
C sends message to B
C(m) m B
Later,
B QUERIESC about message
B m,? C
C DENIESsending message
C(m,?) NO B
5. Denial

7. OSI Security Architecture
(X.800 –Security for Open Systems Interconnection)
•International Standard
•5 Categories
•14 Services

8. OSI Security Architecture
Categories(services)
•Authentication(peer-entity, data-origin)
•Access Control
•Data Confidentiality(connection,
connectionless, selective-field, traffic-flow)
•Data Integrity(connection[recovery,
no-recovery, selective-field],
connectionless[no-recovery,selective-field])
•NonRepudiation(origin, destination)

9. OSI Security Architecture
Authentication
Data Origin (m not protected)
A(m) mB
B(m,A) AUTHENTIC(A)?
Peer Entity
A cB
S(A,B) AUTHENTIC(A,B)?
S(c,masquerador,replay) SECURE(c)?

10. OSI Security Architecture
Access Control
Access REQUEST:
A(m) m{Host/System}
Host MATCHESm to A:
{Host/System}(m,A) m’A
A GRANTED read/write access:
c
A(m’)  {Host/System}

11. OSI Security Architecture
Confidentiality
CONNECTION:
c
K
A  B (e.g. TCP)
CONNECTIONLESS:
A m
KB
SELECTIVE-FIELD:
c
K|c’
A  B
TRAFFIC-FLOW:
A {} B

12. OSI Security Architecture
Integrity
CONNECTION-RECOVERY:
c modification/destruction
A m B(m) recover m
CONNECTION-NO RECOVERY:
c modification/destruction
A m B(m) detect !!
SELECTIVE FIELD:
c modification/destruction
A m|m’B(m) detect(m) !!

13. OSI Security Architecture
Non-Repudiation
SENDER VERIFICATION:
A m,[A]B(m,[A]) mA
RECEIVER VERIFICATION:
A m B
B [m],[B]A([m],[B]) mB

14. OSI Security Architecture
Availability
•Upon request
•Denialof Service
•Attack Countermeasures:
Authentication
Encryption
Physical Response

15. SECURITY MECHANISMS
(X.800) -specific
•Encipherment –unintelligible
•Signature –data tag to ensure
a) Source b) Integrity c) anti-forgery
•Access Control
•Data Integrity
•Authentication
•Traffic Padding –prevent traffic analysis
•Routing Control –adapt upon partial failure
•Notarization –trusted third party

16. SECURITY MECHANISMS
(X.800) -pervasive
•Trusted Functionality
•Security Label
•Event Detection
•Audit Trail
•Recovery

17. ATTACKS
•PASSIVE:
System unaltered,
–hard to detect, easier to prevent
•ACTIVE:
System altered,
–easier to detect, hard to prevent

18. ATTACKS
•PASSIVE:
eavesdropping, monitoring,
message release, traffic analysis
•ACTIVE:
replay, masquerade(impersonation),
modification, denial of service(supression,overload)

19. Block Ciphers 19
Model for Network Security

20. Block Ciphers 20
Model for Network
Access Security
•Gatekeeper: password-based login, screening logic
•Internal controls: monitor activity, analyse stored info