Pre-Shared Keying has a lot of advantages over manual keying. These include endpoint
authentication, which is what the PSKs are really for. It also includes all the benefits of using IKE.
Instead of using a fixed set of encryption keys, session keys will be used for a limited period of
time, where after a new set of session keys are used.
PSK Disadvantages
One thing that has to be considered when using Pre-Shared Keys is key distribution. How are the
Pre-Shared Keys distributed to remote VPN clients and firewalls? This is a major issue, since the
security of a PSK system is based on the PSKs being secret. Should one PSK be compromised, the
configuration will need to be changed to use a new PSK.
Certificates
Each VPN firewall has its own certificate, and one or more trusted root certificates.
The authentication is based on several things:
•
That each endpoint has the private key corresponding to the public key found in its certificate,
and that nobody else has access to the private key.
•
That the certificate has been signed by someone that the remote endpoint trusts.
Advantages of Certificates
A principal advantage of certificates is added flexibility. Many VPN clients, for instance, can be
managed without having the same pre-shared key configured on all of them, which is often the case
when using pre-shared keys and roaming clients. Instead, should a client be compromised, the
client's certificate can simply be revoked. No need to reconfigure every client.
Disadvantages of Certificates
The principal disadvantage of certificates is the added complexity. Certificate-based authentication
may be used as part of a larger public key infrastructure, making all VPN clients and firewalls
dependent on third parties. In other words, there are more aspects that have to be configured, and
there is more that can go wrong.
9.3.4. IPsec Protocols (ESP/AH)
The IPsec protocols are the protocols used to protect the actual traffic being passed through the
VPN. The actual protocols used and the keys used with those protocols are negotiated by IKE.
There are two protocols associated with IPsec, AH and ESP. These are covered in the sections
below.
AH (Authentication Header)
AH is a protocol used for authenticating a data stream.
9.3.4. IPsec Protocols (ESP/AH)
Chapter 9. VPN
404
Summary of Contents for NetDefend DFL-260E
Page 27: ...1 3 NetDefendOS State Engine Packet Flow Chapter 1 NetDefendOS Overview 27...
Page 79: ...2 7 3 Restore to Factory Defaults Chapter 2 Management and Maintenance 79...
Page 146: ...3 9 DNS Chapter 3 Fundamentals 146...
Page 227: ...4 7 5 Advanced Settings for Transparent Mode Chapter 4 Routing 227...
Page 241: ...5 4 IP Pools Chapter 5 DHCP Services 241...
Page 339: ...6 7 Blacklisting Hosts and Networks Chapter 6 Security Mechanisms 339...
Page 360: ...7 4 7 SAT and FwdFast Rules Chapter 7 Address Translation 360...
Page 382: ...8 3 Customizing HTML Pages Chapter 8 User Authentication 382...
Page 386: ...The TLS ALG 9 1 5 The TLS Alternative for VPN Chapter 9 VPN 386...
Page 439: ...Figure 9 3 PPTP Client Usage 9 5 4 PPTP L2TP Clients Chapter 9 VPN 439...
Page 450: ...9 7 6 Specific Symptoms Chapter 9 VPN 450...
Page 488: ...10 4 6 Setting Up SLB_SAT Rules Chapter 10 Traffic Management 488...
Page 503: ...11 6 HA Advanced Settings Chapter 11 High Availability 503...
Page 510: ...12 3 5 Limitations Chapter 12 ZoneDefense 510...
Page 533: ...13 9 Miscellaneous Settings Chapter 13 Advanced Settings 533...
