Transcript IPSec In Depth Encapsulated Security Payload (ESP) • Must encrypt and/or authenticate in each packet • Encryption occurs before authentication • Authentication is applied to.

IPSec In Depth
Encapsulated Security Payload
(ESP)
• Must encrypt and/or authenticate in each
packet
• Encryption occurs before authentication
• Authentication is applied to data in the
IPSec header as well as the data contained
as payload
IPSec Encapsulating Security Payload (ESP)
in Transport Mode
Orig IP Hdr
TCP Hdr
Data
Insert
Append
Orig IP Hdr ESP Hdr TCP Hdr
Data
ESP Trailer ESP Auth
Usually encrypted
integrity hash coverage
SecParamIndex
22-36 bytes total
ESP is IP protocol 50
Seq# InitVector
Padding
Keyed Hash
PadLength NextHdr
© 2000 Microsoft Corporation
IPSec ESP Tunnel Mode
Orig IP Hdr
IPHdr
ESP Hdr IP Hdr
TCP Hdr
Data
TCP Hdr Data
ESP Trailer ESP Auth
Usually encrypted
integrity hash coverage
New IP header with source &
destination IP address
© 2000 Microsoft Corporation
Authentication Header (AH)
• Authentication is applied to the entire
packet, with the mutable fields in the IP
header zeroed out
• If both ESP and AH are applied to a packet,
AH follows ESP
IPSec Authentication Header (AH)
in Transport Mode
Orig IP Hdr
TCP Hdr
Data
Insert
Orig IP Hdr
AH Hdr
TCP Hdr
Data
Integrity hash coverage (except for mutable fields in IP hdr)
Next Hdr Payload Len Rsrv SecParamIndex Seq# Keyed Hash
AH is IP protocol 51
24 bytes total
© 2000 Microsoft Corporation
IPSec AH Tunnel Mode
Orig IP Hdr
IP Hdr
TCP Hdr
AH Hdr Orig IP Hdr
Data
TCP Hdr
Data
Integrity hash coverage (except for mutable new IP hdr fields)
New IP header with source &
destination IP address
© 2000 Microsoft Corporation
Internet Key Exchange (IKE)
• Phase I
– Establish a secure channel(ISAKMP SA)
– Authenticate computer identity
• Phase II
– Establishes a secure channel between
computers intended for the transmission of data
(IPSec SA)
Main Mode
• Main mode negotiates an ISAKMP SA
which will be used to create IPSec Sas
• Three steps
– SA negotiation
– Diffie-Hellman and nonce exchange
– Authentication
Main Mode (Kerberos)
Initiator
Responder
Header, SA Proposals
Header, Selected SA Proposal
Header, D-H Key Exchange, Noncei,
Kerberos Tokeni
Encrypted
Header, D-H Key Exchange, Noncer,
Kerberos Tokenr
Header, Idi, Hashi
Header, Idr, Hashr
Main Mode (Certificate)
Initiator
Responder
Header, SA Proposals
Header, Selected SA Proposal
Header, D-H Key Exchange, Noncei
Header, D-H Key Exchange,
Noncer,Certificate Request
Encrypted
Header, Idi, Certificatei, Signaturei,
Certificate Request
Header, Idr, Certificater,
Signaturer
Main Mode (Pre-shared Key)
Initiator
Responder
Header, SA Proposals
Header, Selected SA Proposal
Header, D-H Key Exchange, Noncei
Header, D-H Key Exchange, Noncer
Encrypted
Header, Idi, Hashi
Header, Idr, Hashr
Quick Mode
• All traffic is encrypted using the ISAKMP
Security Association
• Each quick mode negotiation results in two
IPSec Security Associations (one inbound,
one outbound)
Quick Mode Negotiation
Initiator
Responder
Encrypted
Header, IPSec Proposed SA
Header, IPSec Selected SA
Header, Hash
Header, Connected Notification