Configuring Advanced Ike Setup - ZyXEL Communications ZYWALL2 ET 2WE User Manual

ZyWALL 2 Series User's Guide
14.12.5 Perfect Forward Secrecy (PFS)
Enabling PFS means that the key is transient. The key is thrown away and replaced by a brand new key using
a new Diffie-Hellman exchange for each new IPSec SA setup. With PFS enabled, if one key is compromised,
previous and subsequent keys are not compromised, because subsequent keys are not derived from previous
keys. The (time-consuming) Diffie-Hellman exchange is the trade-off for this extra security.
This may be unnecessary for data that does not require such security, so PFS is disabled (None) by default in
the ZyWALL. Disabling PFS means new authentication and encryption keys are derived from the same root
secret (which may have security implications in the long run) but allows faster SA setup (by bypassing the
Diffie-Hellman key exchange).

14.13 Configuring Advanced IKE Setup

Select one of the VPN rules in the VPN Rules screen and click Edit to configure the rule's settings. The
basic IKE rule setup screen opens
Set the Key Management (or IPSec Keying Mode) field to IKE and click the Advanced button to display
the advanced IKE VPN rule setup screen.
14-24 VPN Screens