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Internet Security CSCE 813 IPsec. CSCE813 - Farkas2 TCP/IP Protocol Stack Application Layer Transport Layer Network Layer Data Link Layer.

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Presentation on theme: "Internet Security CSCE 813 IPsec. CSCE813 - Farkas2 TCP/IP Protocol Stack Application Layer Transport Layer Network Layer Data Link Layer."— Presentation transcript:

1 Internet Security CSCE 813 IPsec

2 CSCE813 - Farkas2 TCP/IP Protocol Stack Application Layer Transport Layer Network Layer Data Link Layer

3 CSCE813 - Farkas3 Network Layer Provides connectionless service Routing (routers): determine the path a path has to traverse to reach its destination Defines addressing mechanism – Hosts should conform to the addressing mechanism

4 CSCE813 - Farkas4 Communication Between Layers Transport layer Network layer Data Link layer Network layer Data Link layer Network layer Data Link layer Network layer Transport layer Application layer Application Data Transport payload Network Payload Data Link Payload Host ARouter Host B

5 CSCE813 - Farkas5 Network Layer and Security In most network architecture and corresponding communication protocol stack: network layer protocol data units are transmitted in the clear: Easy to inspect the data content Easy to forge source or destination address Easy to modify content Easy to replay data Need network layer security protocol

6 CSCE813 - Farkas6 Network Layer Protocols Several protocols have been proposed: Security Protocol 3 (SP3): U.S. NSA and NIST as part of the secure data network system (SDNS) Network Layer Security Protocol (NLSP): ISO for Connectionless Network Protocol (CLNP) Integrated NLSP (I-NLSP): NIST, for both IP and CLNP swIPe: John Ioannidis and Matt Blaze at Berkley Univ. Used in Unix environment

7 CSCE813 - Farkas7 Internet Engineering Task Force Standardization IPv6 development requirements: Strong security features – Security features algorithm-independent – Must enforce wide variety of security policies – Avoid adverse impact on Internet users who do not need security 1992: IPSEC WG (IETF) – Define security architecture – Standardize IP Security Protocol and Internet Key Management Protocol 1998: revised version of IP Security Architecture – IPsec protocols (two sub-protocols AH and ESP) – Internet Key Exchange (IKE)

8 CSCE813 - Farkas8 IPsec Provides security for IP and upper layer protocols Suit of algorithms: – Mandatory-to-implement – Assures interoperability – Easy to add new algorithms

9 CSCE813 - Farkas9 IP Security Overview IPSec: method of protecting IP datagrams – Data origin authentication – Connectionless data integrity authentication – Data content confidentiality – Anti-replay protection – Limited traffic flow confidentiality

10 CSCE813 - Farkas10 IP Security Architecture IPsec module 1 IPsec module 2 SPD SAD SPD IKE IPsec SA

11 CSCE813 - Farkas11 Security Association Associates security services and keys with the traffic to be protected – Identified by Security Parameter Index (SPI)  retrieve correct SA parameters from Security Association Database (SAD) – Ipsec protocol identifier – Destination address (direction) Simplex connection  need to establish two SAs for secure bidirectional communication

12 CSCE813 - Farkas12 Security Association Defines security services and mechanisms between two end points (or IPsec modules): – Hosts – Network security gateways (e.g., routers, application gateways) – Hosts and security gateways Security service, parameters, mode of operation, and initialization vector – e.g., Confidentiality using ESP with DES in CBC mode with IV initialization vector

13 CSCE813 - Farkas13 Security Association May use either Authentication Header (AH) or Encapsulating Security Payload (ESP) but not both  if both AH and ESP are applied, need two SAs Bundle: set of SAs through which traffic must be processed

14 CSCE813 - Farkas14 SA -- Lifetime Amount of traffic protected by a key and time frame the same key is used – Manual creation: no lifetime – Dynamic creation: may have a lifetime

15 CSCE813 - Farkas15 SA -- Security Granularity User (SSO) specified Host-oriented keying – All users on one host share the same session key – Not recommended! User-oriented keying – Each user on one host have one or of more unique session keys Session-unique keying – Single session key is assigned to a give IP address, upper-layer protocol, and port number

16 CSCE813 - Farkas16 Security Policy Database (SPD) Defines: – What traffic to be protected – How to protect – With whom the protection is shared For each packet entering or leaving an IPsec implementation SPD is used to determine security mechanism to be applied Actions: – Discard: do not let packet in or out – Bypass: do not apply or expect security services – Protect: apply/expect security services on packets

17 CSCE813 - Farkas17 Anti-replay Protection Not explicitly part of the architecture Protection by sequence number (32-bits) and sliding receive window (64-bits) When SA is created: sequence number is initiated to zero Prior to IPsec output processing: sequence number is incremented Packet stream Sliding window of received packets 0 0011111111111111 NN+5 N+7 New packet

18 CSCE813 - Farkas18 IPSec Protection for IP and upper layer protocols IPSec protocols – Encapsulating Security Payload (ESP) Proof of data origin, data integrity, anti-replay protection Data confidentiality and limited traffic flow confidentiality – Authentication Header (AH) Proof of data origin, data integrity, anti-replay protection

19 CSCE813 - Farkas19 IPsec Security provided by ESP or AH is dependent on the cryptographic algorithms applied to them Default encryption algorithm: DES CBC – Not suited for highly sensitive data or – For data that must remain secure for extended period of time Authentication and/or confidentiality requires shared keys Manual key addition is supported but scales poorly Internet Key Exchange (IKE): key management protocol

20 CSCE813 - Farkas20 AH and ESP Transport mode: protect upper layer protocols – IPSec header is inserted between the IP header and the upper-layer protocol header – Communication endpoints must be cryptographic endpoints IP IPsec Payload protected

21 CSCE813 - Farkas21 AH and ESP Tunnel mode: protect entire IP datagram – Entire IP packet to be protected is encapsulated in another IP datagram and an IPsec header is inserted between the outer and inner IP headers Payload IPIPsecIP protected Original IP header New IP header

22 CSCE813 - Farkas22 Authentication Header (AH) Does NOT provide confidentiality Provides: – Data origin authentication – Connectionless data integrity May provide: – Non-repudiation (depends on cryptographic alg.) – Anti-replay protection Precision of authentication: granularity of SA Protocol number: 51

23 CSCE813 - Farkas23 AH Protected IP packet Protected dataAH header IP header authenticated

24 CSCE813 - Farkas24 AH Header 32 bit Authentication data (n*32 bit) Sequence number Security Parameter Index Next header Payload length Reserved

25 CSCE813 - Farkas25 Authentication Data Computed by using – authentication algorithm (MD5, SHA-1) – cryptographic key (secret key) Sender: computes authentication data Recipient: verifies data

26 CSCE813 - Farkas26 Encapsulating Security Payload (ESP) Provides: – Confidentiality – Authentication (not as strong as AH: IP headers below ESP are not protected) – Limited traffic flow confidentiality – Anti-replay protection Protocol number: 50

27 CSCE813 - Farkas27 ESP Protected IP packet ESP Trailer Protected data ESP headerIP header authenticated encrypted

28 CSCE813 - Farkas28 ESP header and trailer ESP packet processing: 1. Verify sequence number 2. Verify integrity 3. Decrypt ESP header: not encrypted – Contains: SPI and sequence number ESP trailer: partially encrypted – Contains: padding, length of padding, next protocol, authentication data

29 CSCE813 - Farkas29 ESP Format Authentication data (n*32 bit) Sequence number Security Parameter Index padding Next headerPad length padding Payload data Confidentiality protected Authen- ticity protected

30 CSCE813 - Farkas30 ESP SA has multiple algorithms defined: – Cipher: for confidentiality – Authenticator: for authenticity – Each ESP has at most: one cipher and one authenticator or one cipher and zero authenticator or zero cipher and one authenticator or Disallowed: zero cipher and zero authenticator or

31 CSCE813 - Farkas31 Encryption Block ciphers in Cipher Block Chain (CBC) mode Need – Padding at the end of data – Initialization vector (IV) – contained in the packet

32 CSCE813 - Farkas32 Encryption and Compression Interdependence between encryption and compression – When encryption is applied at Internet layer  prevents effective compression by lower protocol layers – IPsec: does not provide data compression

33 CSCE813 - Farkas33 Key Management Protocols IP security architecture supports manual and automated SA and key agreement Key management protocol: e.g., IKE Proposals for automated key management protocol


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