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A collection of protocols used to create VPNs |
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A network layer security protocol providing
cryptographic security services
that can support various combinations of authentication, integrity,
access control, and confidentiality |
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Allows creation of an encrypted tunnel between
two private networks |
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Supports authentication of the two ends of the
tunnel |
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Cannot directly encrypt non-IP traffic |
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Can encrypt GRE tunnel containing non-IP data |
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Comprises of IKE, ESP, and AH |
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LAN-to-LAN or site-to-site |
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Used to connect two private networks to form one
combined virtual private network |
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Remote-access client IPsec |
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Used to allow road warriors to be part of the
trusted network |
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Internet Key Exchange (IKE) protocol |
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For negotiating security parameters and
establishing authenticated keys |
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Uses UDP port 500 for ISAKMP |
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Encapsulating Security Payload (ESP) protocol |
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For encrypting, authenticating, and securing
data |
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IP protocol 50 |
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Authentication Header (AH) protocol |
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For authenticating and securing data |
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IP protocol 51 |
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Negotiates
IPsec tunnel characteristics
between two IPsec peers |
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Negotiates IPsec protocol parameters |
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Exchanges public keys |
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Authenticates both sides |
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Manages keys after the exchange |
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Automates entire key-exchange process |
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Identify interesting traffic by an IPsec peer
that has been configured to initiate an IPsec session for this traffic |
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IPsec peers negotiate a secure authenticated
communication channel using main mode or aggressive mode negotiation, resulting in creation of an IKE Security
Association (SA) between the two IPsec peers (IKE phase I) |
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Create two IPsec SAs between the two IPsec peers
via IKE quick mode negotiation (IKE phase II) |
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Send data over encrypted tunnel using ESP and/or
AH encapsulation |
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Agreeing on a set of parameters that are to be
used to authenticate the two peers |
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Agreeing on parameters used to encrypt a portion
of the main mode and all of the quick mode messages |
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None of the aggressive mode messages are
encrypted |
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Authenticate the two peers to each other |
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Generate keys used to generate keying material
for subsequent encryption of data |
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All of the parameters negotiated and the keys
used to generate keys for encryption are stored as IKE or ISAKMP security
association (SA) |
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Main mode using preshared key authentication
followed by quick mode negotiation |
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Main mode using digital signature authentication
followed by quick mode negotiation |
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Aggressive
mode using preshared key authentication followed by quick mode
negotiation |
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Main mode using nonces authentication followed
by quick mode negotiation |
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Aggressive
mode using digital signature authentication followed by quick mode
negotiation |
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To have two peers agree on a set of attributes
for creating the IPsec security associations that could be used by ESP to
encrypt the data |
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To redo Diffie-Hellman (DH) exchange so that new
keying material can be used to generate IPsec encryption keys |
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Used in IKE by two peers to generate a shared DH
secret and to generate keying material for later use |
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DH secret also used with preshared secret to
authenticate two peers to each other |
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There exists Xa such that Xa
= ga mod p where g is the generator, p is a large prime number,
and a is a private secret known only to the initiator |
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There exists Xb such that Xb
= gb mod p where g is the generator, p is a large prime number,
and b is a private secret known only to the responder |
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Initiator and responder can generate a shared
secret known only to the two of them by exchanging the values Xa
and Xb with each other |
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Initiator secret = (Xb)a
mod p = (Xa)b mod p = responder secret = gab |
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IKE SA established |
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Main mode using preshared key authentication
completed |
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Quick mode will be used to negotiate parameters
of IPsec SA |
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Negotiate parameters of IPsec SA |
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Perfect Forward Secrecy (PFS) may be used by
initiator to request that a new DH secret be generated over an encrypted
channel |
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New nonces generated: Ni` and Nr` |
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New DH public values: |
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Xa`=ga mod p |
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Xb`=gb mod p |
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Both peers generate new DH shared secret = (Xb`)a
mod p = (Xa`)b
mod p |
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Both peers generate shared session keys for
incoming and outgoing IPsec SAs based on SKEYID_d, new DH shared secret,
SPI, and Ni` and Nr` |
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Preshared keys |
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Digital signatures |
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Encrypted nonces |
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Data Encryption Standard (DES) |
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Triple DES (3DES) |
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Transport mode |
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Tunnel mode |
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Notes