1. IPSecurity

2. Overview
The Internet community has developed application-specific security mechanisms in a number of application areas, including electronic mail (S/MIME, PGP), client/server (Kerberos), Web access (Secure Sockets Layer), and others.
However, users have some security concerns that cut across protocol layers.
For example, an enterprise can run a secure, private TCP/IP network by disallowing links to untrusted sites, encrypting packets that leave the premises, and authenticating packets that enter the premises.
By implementing security at the IP level, an organization can ensure secure networking not only for applications that have security mechanisms but also for the many security-ignorant applications.

3. IP Security..___...____...._____.....______...........
Functional Areas
Authentication
Confidentiality
Key Management

4. IP Security
Authentication mechanism assures that a received packet was, in fact, transmitted by the party identified as the source in the packet header.
In addition, this mechanism assures that the packet has not been altered in transit.
Confidentiality facility enables communicating nodes to encrypt messages to prevent eavesdropping by third parties.
The key management facility is concerned with the secure exchange of keys.

5. Applications of IP Security..___...___....____...........
Provide Secure Connection Across 1
MAN
LAN
WAN

6. Applications of IP Security..___...___....____...........
Secure Remote Access over the Internet 2

7. Applications of IP Security..___...___....____...........
Establish Extranet and Intranet connectivity 3

8. Applications of IP Security..___...___....____...........
Enhancing Electronic commerce security 4

9. Applications of IP Security..___...___....____...........
Router Applications
Router Advertisement (new)
Router Advertisement (maintenances)
Not forged update

10. Benefits of IP Security..___..._____....______...........
IPsec in Router
IPsec in Firewall
Its below transport layer, so no need to change existing security mechanism
Transparent to End-user
IPsec for individual users

11. IPSecirity Scenario

12. IP Security Architecture..___..._____...._____...........
RFC 2401: An overview of security architecture
RFC 2402: Packet Authentication Extension
RFC 2406: Packet Encryption Extension
RFC 2408: Key Management capabilities
Two security Header Extension
Encapsulating Security Payload (ESP)
Authentication Header (AH)
services
Access control
Connectionless integrity
Data origin authentication
Rejection of replayed packets
Confidentiality (encryption)
Limited traffic flow confidentiality

13. IPSec Services
IPSec provides security services at the IP layer by enabling a system to select required security protocols, determine the algorithm(s) to use for the service(s), and put in place any cryptographic keys required to provide the requested services.
Two protocols are used to provide security:
An authentication protocol designated by the header of the protocol, Authentication Header (AH); and
A combined encryption/authentication protocol designated by the format of the packet for that protocol, Encapsulating Security Payload (ESP).

14. Security Association…___...._____.....______...........
A one-way relationship between sender & receiver
Uniquely identified by:
SA Parameters
Security Parameters Index (SPI)
IP Destination Address
Security Protocol Identifier
A bit string assigned to this SA. Carried in AH and ESP to enable the receiver to select SA.
The address of the destination endpoint of the SA.
Indicates whether the association is an AH or ESP Security Association.
Sequence Number Counter
Sequence Counter Overflow
Path MTU
AH Information
ESP Information
Anti-Replay Window
IP Security Mode
Lifetime of this Security Association

15. IPSec Modes Transport Mode
Transport Mode provides a secure connection between two endpoints as it encapsulates IP's payload.
Tunnel Mode
Tunnel Mode encapsulates the entire IP packet to provide a virtual "secure hop" between two gateways.
Used to form a traditional VPN, where the tunnel generally creates a secure tunnel across an un-trusted Internet.

16. Authentication Header…__......___........_____...........
Provides support for Data Integrity and Authentication
Ensures that modification to a packet content in transit is not possible.
Enables End-System to Authenticate the User or Application
Prevents Address Spoofing Attack
Guards against reply attack

17. Authentication Header…__......___........_____...........
Data integrity
Authentication
Reply Protection
MAC
Secret shared key
Sequence Number

18. Authentication Header…__......___........_____...........
Fields:
Next Header: Identify the type of header immediately following this header
(could be TCP or UDP header, based on application)
Payload Length: Length of authentication header in 32 bit word minus 2
Reserved: For future use (set to 0)
Security Parameter index: Identifies Security Association Rules
Sequence Number: Monotonically increasing counter value(number of messages
Sent using the current SA)
Authentication Data: Contains Integrity Check Value(ICV), Eg. MAC

19. Authentication Header…__......___........_____...........

20. Authentication Header…__......___........_____...........
ICV (Integrity Check Value)
It’s a Message Authentication Code
Calculated over the entire packet — including most of the headers.
The recipient recomputes the same hash; Mismatched values mark the packet as either damaged in transit, or not having the proper secret key. These are discarded.

21. Authentication Header…__......___........_____...........
Anti-Reply Service
Protects against Reply Attack
Based on Sequence Number
Sequence number cycle : 232 – 1
When this limit is reached, negotiate new SA
Inbound processing when a packet is received

22. Authentication Header…__......___........_____...........
Transport Mode
IP Header
TCP
Data
IP Header AH
TCP
Data

23. Authentication Header…__......___........_____...........
Tunnel Mode
IP Header
TCP
Data
New IP Header AH
Original IP Header
TCP
Data

24. Encapsulating Security Payload.....__......___..........
Fields:
Next Header: Identify the type of header immediately following this header
(could be TCP or UDP header, based on application)
Security Parameter index: Identifies Security Association Rules
Sequence Number: Monotonically increasing counter value(number of messages
Sent using the current SA)
Payload Data: Transport level data or IP packet
Padding: Bytes
Pad Length: number of pad bytes
Authentication Data: Contains Integrity Check Value(ICV)

25. Encapsulating Security Payload.....__......___..........

26. Encapsulating Security Payload.....__......___..........
Transport Mode
IP Header
TCP
Data
IP Header
ESP
TCP
Data
ESP Trailer
ESP Authentication
Encrypted

27. Encapsulating Security Payload.....__......___..........
Tunnel Mode

28. Combining Security Association.....__......___..........
Individual SA can implement either the AH or ESP protocol but not both.
Some traffic flow require services provided by both AH & ESP
Security Association Bundle: It refers to a sequence of SAs through which traffic must be processed
to provide a desired set of IPSec services.
The SAs in a bundle may terminate at different or same end-points
Security Association Bundle
Transport Adjacency:
Refers to applying more than one security protocol to the same IP packet, without invoking tunneling.
Iterated tunneling:
Refers to the application of multiple layers of security protocols effected through IP tunneling. Each tunnel can originate or terminate at a different IPSec site along the path.

29. Combining Security Association.....__......___..........
Transport Adjacency:

30. Combining Security Association.....__......___..........
Iterated tunneling:

31. Combining Security Association.....__......___..........
Iterated tunneling with different End Point:

32. Combining Security Association.....__......___..........
Authentication Plus Confidentiality
Transport mode ESP:
Authentication and Encryption apply to the IP payload,
IP header is not protected.
Tunnel mode ESP:
Applies to entire IP packet.
Possible Combinations:
a: AH in transport mode
b: ESP in transport mode
c: ESP followed by AH in transport mode
d: a, b, c inside an AH or ESP in tunnel mode

33. Key Management......_____.........______..........
Oakley Key Determination Protocol
Refinement over Diffie-Hellman key exchange algorithm
Features:
Secret keys are created only when needed
Requires no pre-existing infrastructure
Weaknesses:
Doesn’t provide any info regarding identity of parties
Subject to man in the middle attack

34. Key Management......_____.........______..........
Man in the Middle Attack
Clogging Attack

35. Key Management......_____.........______..........
Oakley
Features
Cookies to thwart clogging attack
Enables two parties to negotiate group
Use nonces to ensure against reply attack

36. Key Management......_____.........______..........
Oakley
Authentication Methods
Digital Signature
Public key Encryption
Symmetric key Encryption