IPSEC : KEY MANAGEMENT PRESENTATION BY: SNEHA A MITTAL(121427) NISHU RASTOGI (121418) BHOOMIKA PARMAR (121406) MONIKA MITTAL (121414) ROHIT JAIN (121424) SUBMITTED TO: Dr. C. RAMAKRISHNA (ASSOCIATE PROFESSOR) (CSE DEPARTMENT) NITTTR CHANDIGARH

overview KEY MANAGEMENT FOR IPSEC TYPES OF KEY MANAGEMENT ISAKMP/OAKLEY OAKLEY KEY DETERMINATION PROTOCOL DIFFIE HELLMAN KEY EXCHANGE FEATURES ISAKMP PAYLOAD TYPES CONCLUSION

KEY MANAGEMENT FOR IPSEC The key management portion of IPSec involves the determination and distribution of secret keys. A typical requirement is four keys for communication between two applications: transmit and receive pairs for both AH and ESP.

TYPES Two types of key management according to the IPSec Architecture document : Manual Automated.

Manual A system administrator manually configures each system with its own keys and with the keys of other communicating systems. This is practical for small, relatively static environments.

Automated An automated system enables the on-demand creation of keys for SAs Facilitates the use of keys in a large distributed system with an evolving configuration.

ISAKMP/OAKLEY The default automated key management protocol for IPSec is referred to as ISAKMP/Oakley Consists of the following elements: Oakley Key Determination Protocol Internet Security Association and Key Management Protocol (ISAKMP)

OAKLEY KEY DETERMINATION PROTOCOL Oakley is a refinement of the Diffie-Hellman key exchange algorithm but providing added security. Oakley is generic in that it does not dictate specific formats. Oakley KDP = Diffie-Hellman Key Exchange + authentication & cookies

DIFFIE HELLMAN KEY EXCHANGE A & B agree on 2 numbers n and g (g is primitive relative mod (n)) A chooses a large random number x & calculates X = gx mod (n) {A Sends X, g, and n to B} B chooses a large random number y & calculates Y = gy mod (n) {Then B sends Y to A} Finally A calculates k = Yx mod (n) & B calculates k’ = Xy mod (n)

DIFFIE HELLMAN KEY EXCHANGE Features: Secret keys are created only when needed. Exchange requires no pre existing infrastructure Weaknesses: Don’t provide info about identities of parties Man – in – the – middle attack can be done.

features Five main features of Oakley Cookies help resist clogging attacks Enables two parties to negotiate a group. Nonce helps resist message replay attacks Enables exchange of Diffie Helman Public key values Authentication helps resist man-in-the-middle attacks

CLOGGING ATTACKS A form of denial of service attacks Attacker sends a large number of public key Yi in crafted IP packets, forcing the victim’s computer to compute secret keys Ki = YiX mod p over and over again Diffie-Hellman is computationally intensive because of modular exponentiations

PREVENTING CLOGGING ATTACKS USING COOKIES Cookies help Before doing computation, recipient sends a cookie (a random number) back to source and waits for a confirmation including that cookie This prevents attackers from making DH requests using crafted packets with crafted source addresses

GROUPS GROUPS SUPPORTED: Modular exponentiation with a 768-bit modulus Elliptic curve group over 2155 Elliptic curve group over 2185

NONCES NONCES: NONCE is a locally generated pseudo random numbers Nonces appear in responses & are encrypted during certain portions of key exchange to secure their user

AUTHENTICATION METHODS USED IN OAKLEY Digital Signatures Public Key Encryption Secret Key Encryption

ISAKMP ISAKMP provides A framework for Internet key management The specific protocol support, including formats, for negotiation of security attributes. ISAKMP by itself does not dictate a specific key exchange algorithm rather, ISAKMP consists of a set of message types that enable the

ISAKMP Rather ISAKMP consists of a set of message types that enable the use of a variety of key exchange algorithms. Oakley is the specific key exchange algorithm mandated for use with the initial version of ISAKMP.

ISAKMP ISAKMP: Internet Security Association and Key Management Protocol Specifies key exchange formats Each type of payload has the same form of a payload header ISAKMP header

ISAKMP Payload Types SA: for establishing a security association Proposal: for negotiating an SA Transform: for specifying encryption and authentication algorithms Key-exchange: for specifying a key-exchange algorithm Identification: for carrying info and identifying peers Certificate-request: for requesting a public-key certificate

ISAKMP Payload Types Certificate: contain a public-key certificate Hash: contain the hash value of a hash function Signature: contain the output of a digital signature function Nonce: contain a nonce Notification: notify the status of the other types of payloads Delete: notify the receiver that the sender has deleted an SA or SAs 8-bit Next payload Reserved 16-bit Payload length

CONCLUSION The default automated key management protocol for IPsec is referred to as ISAKMP/Oakley Oakley is a refinement of the Diffie-Hellman key exchange algorithm but providing added security. ISAKMP provides a framework for Internet key management

REFERENCES Cryptography And Network Security - Principles And Practice, Fourth Edition, “William Stallings”

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