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

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OVERVIEW

KEY MANAGEMENT FOR IPSEC

TYPES OF KEY MANAGEMENT

ISAKMP/OAKLEY

OAKLEY KEY DETERMINATION PROTOCOL

DIFFIE HELLMAN KEY EXCHANGE

FEATURES

ISAKMP

PAYLOAD TYPES

CONCLUSION

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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.

KEY MANAGEMENT FOR IPSEC

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Two types of key management

according to the IPSec

Architecture document :

Manual

Automated.

TYPES

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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.

MANUAL

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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.

AUTOMATED

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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)

ISAKMP/OAKLEY

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 8

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)

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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.10

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 11

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

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PREVENTING CLOGGING ATTACKS USING COOKIES

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Cookies helpBefore 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

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o GROUPS SUPPORTED:

• Modular exponentiation with a 768-bit

modulus

• Modular exponentiation with a 1024-bit

modulus

• Modular exponentiation with a 1536-bit

modulus

• Elliptic curve group over 2155

• Elliptic curve group over 2185

NONCES

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o 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

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Digital SignaturesPublic Key EncryptionSecret Key Encryption

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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 the18

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. 19

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 header20

ISAKMP PAYLOAD TYPES

SA: for establishing a security associationProposal: for negotiating an SATransform: for specifying encryption and

authentication algorithmsKey-exchange: for specifying a key-

exchange algorithm Identification: for carrying info and

identifying peersCertificate-request: for requesting a public-

key certificate 21

ISAKMP PAYLOAD TYPES

Certificate: contain a public-key certificateHash: contain the hash value of a hash

functionSignature: contain the output of a digital

signature functionNonce: contain a nonceNotification: notify the status of the other

types of payloadsDelete: notify the receiver that the sender

has deleted an SA or SAs 8-bit

Next payload8-bit

Reserved 16-bit

Payload length

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CONCLUSION

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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

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

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THANK YOU