1. ISAKMP
RFC 2408
Internet Security Association & Key Management Protocol
Protocol
Establish, modify, and delete SAs
Negotiate crypto keys
Procedures
Authentication of peers
Threat mitigation

2. ISAKMP Defines procedures and packet formats to deal with SAs and keys
Provides a framework for secure communication on the Internet
Does not specify algorithms, formats, or protocols
ISAKMP is a framework in which a specific secure communication definition can be implemented

3. ISAKMP Security Associations Authentication Public Key Cryptography
Protection
DoS – Anti-Clogging
Hijacking a connection
Man in the middle attacks

4. ISAKMP Terminology
DOI – Domain Of Interpretation: defines payload formats, exchange types, naming conventions

5. IISAKMP – Phases
Phase 1: Two entities agree on how to protect further negotiation traffic. They negotiate an ISAKMP SA for an authenticated and secure channel
Phase 2:The phase 1 secure channel is used to negotiate security services for IPSec.

6. ISAKMP Header Initiator Cookie Responder Cookie Major Version Minor
Next Payload
Exchange Type
Flags
Message ID
Length

7. Header Fields
Initiator Cookie (8 octets) – Cookie of entity that initiated SA establishment, notification or deletion.
Responder Cookie (8 octets) – Cookie of the responder
Next Payload (1 octet) – Type of first payload
Major/Minor Version (4 bits each) – Version of ISAKMP in use
Exchange Type (1 octet) – Type of exchange being used
Flags (1 octet) – More stinking flags, encrypt, commit authentication only
Message ID (4 octets) – Unique ID to identify things in Phase 2
Length (4 octets) – Length of total message (headers + payloads)

8. Next Payload Types Next Payload Type Value Next Payload Type Value
NONE 0
SA 1
Proposal 2
Transform 3
Key Exchange 4
Identification 5
Certificate 6
Cert Request 7
Next Payload Type Value
Hash 8
Signature 9
Nonce 10
Notification 11
Delete 12
Vendor ID 13
Reserved 14 – 127
Private Use

9. Exchange Types Exchange Type Value Exchange Type Value
NONE 0
Base 1
Id Protection 2
Auth Only 3
Aggressive 4
Informational 5
Exchange Type Value
ISAKMP Future Use
DOI Specific Use 32 – 127
Private Use

10. Generic Payload Header
Next Payload
Reserved
Payload Length
Payload Data

11. Domain of Interpretation (DOI)
SA Payload
Next Payload
Reserved
Payload Length
Domain of Interpretation (DOI) ~
Situation
DOI (4 octets) – Identifies the DOI under which this negotiation is taking place. A value of 0 (zero) during Phase 1 specifies a Generic ISAKMP SA which can be used for any protocol during Phase 2.
Situation - A DOI-specific field that identifies the situation under which this negotiation is taking place.

12. Proposal Payload Next Payload Reserved Payload Length Proposal No.
Proposal ID
SPI Size
No. of Transforms
SPI (variable)

13. Proposal Payload
Payload Length (2 octets) – Length is octets of the entire Proposal payload including the generic payload header, the Proposal payload, and all Transform payloads associated with this proposal.
Proposal No. - Identifies the Proposal number for the current payload.
Proposal ID – Specifies the protocol identifier such as IPSEC ESP, IPSEC AH, OSPF, TLS, etc.
SPI Size – Length in octets of the SPI as defined by the Protocol ID.
No. of Transforms – Specifies the number of transforms for the proposal.
SPI (variable) – The sending entity's SPI.

14. Transform Payload ~ Next Payload Reserved Payload Length Transform No.
Transform ID
Reserved2 ~
SA Attributes

15. Transform Payload
Payload Length (2 octets) – Length is octets of the current payload, including the generic payload header, Transform values, and all SA attributes
Transform No. - Identifies the Transform number for the current payload.
Transform ID – Specifies the Transform identifier fmor the protocol within the current proposal.
Reserved 2 (2 octets) – Set to zero.
SA Attributes (Variable length) – SA attributes should be represented using the Data Attributes format.

16. Key Exchange Payload ~ Reserved Payload Length Next Payload
Key Exchange Data
Key Exchange Data (variable length) – Data required to generate a session key. This data is specified by the DOI and the associated Key Exchange algorithm.

17. Certificate Payload ~ Reserved Payload Length Next Payload
Cert Encoding
Key Exchange Data ~
Cert Encoding (1 octet) – Indicates the type of certificate contained in the Certificate field.

18. Certificate Types Certificate Type Value Certificate Type Value NONE 0
PKCS #7 1
PGP Certificate 2
DNS Signed Key 3
X.509 Cert - Signature 4
X.509 Cert – Key Exchange 5
Certificate Type Value
Kerberos Token 6
Cert Revoc List 7
Authority Revoc List 8
SPKI Cert. 9
X.509 Cert – Attribute 10
Reserved

19. Other Payloads ~ ~ ~ Reserved Payload Length Next Payload Hash Data
Signature Data
Next Payload
Reserved
Payload Length ~
Nonce Data

20. Notification Payload ~ ~ Next Payload Reserved Payload Length DOI
Protocol ID
SPI Size
Notify Message Type ~
SPI ~
Notification Data

21. Notify Messages Errors Value INVALID-PAYLOAD-TYPE 1
DOI-NOT-SUPPORTED
SITUATION-NOT-SUPPORTED
INVALID-COOKIE
INVALID-MAJOR-VERSION
INVALID-MINOR-VERSION
INVALID-EXCHANGE-TYPE
INVALID-FLAGS
INVALID-MESSAGE-ID
INVALID-PROTOCOL-ID
INVALID-SPI
INVALID-TRANSFORM-ID
ATTRIBUTES-NOT-SUPPORTED
NO-PROPOSAL-CHOSEN
BAD-PROPOSAL-SYNTAX
Errors Value
PAYLOAD-MALFORMED
INVALID-KEY-INFORMATION
INVALID-ID-INFORMATION
INVALID-CERT-ENCODING
INVALID-CERTIFICATE
CERT-TYPE-UNSUPPORTED
INVALID-CERT-AUTHORITY
INVALID-HASH-INFORMATION
AUTHENTICATION-FAILED
INVALID-SIGNATURE
ADDRESS-NOTIFICATION
NOTIFY-SA-LIFETIME
CERTIFICATE-UNAVAILABLE
UNSUPPORTED-EXCHANGE-TYPE
UNEQUAL-PAYLOAD-LENGTHS
RESERVED (Future Use)
Private Use – 16383

22. ISAKMP Message Construction
Initiator Cookie
Responder Cookie
Major
Version
Minor
Version
NP = KE
Exchange Type
Flags
Message ID
Total Message Length
NP = Nonce
Reserved
KE Payload Length
Key Exchange Data
NP = 0
Reserved
Nonce Payload Length
Nonce Data

23. Proposal Syntax Proposal # Proposals with the same Proposal
Transform #
Proposals with the same Proposal
number are taken as a logical AND.
Proposals with different numbers are
taken as a logical OR.
Different Transform within a proposal
are taken as a logical OR.

24. Proposal Example Proposal 1: AH Transform 1: HMAC-SHA
Transform 2: HMAC-MD5
Proposal 2: ESP
Transform 1: 3DES with HMAC-SHA
Transform 2: 3DES with HMAC-MD5
Transform 3: AES with HMAC-SHA-256
Proposal 3: ESP
Proposal 4: PCP
Transform 1: LZS

25. Exchange Types Exchange Type Value Exchange Type Value
NONE 0
Base 1
Id Protection 2
Auth Only 3
Aggressive 4
Informational 5
Exchange Type Value
ISAKMP Future Use
DOI Specific Use 32 – 127
Private Use

26. Base Exchange Initiator Direction Responder Note
Header, SA, Nonce => Begin ISAKMP-SA negotiation
<= HDR, SA, Nonce Basic SA agreed upon
Header, KE, Idii, Auth => Key generated by responder
Initiator Ident verified
<= HDR, KE, Idir, Auth Responder Ident verified
Initiator key generated, SA est.