ZyXEL Communications ZYWALL USG 2000 Manual page 347

Table 107 VPN > IPSec VPN > VPN Connection > Edit (continued)
LABEL
Encryption
Authentication
Add icon
Perfect
Forward
Secrecy (PFS)
Connectivity
Check
Enable
Connectivity
Check
ZyWALL USG 2000 User's Guide
DESCRIPTION
This field is applicable when the Active Protocol is ESP. Select which
key size and encryption algorithm to use in the IPSec SA. Choices
are:
NULL - no encryption key or algorithm
DES - a 56-bit key with the DES encryption algorithm
3DES - a 168-bit key with the DES encryption algorithm
AES128 - a 128-bit key with the AES encryption algorithm
AES192 - a 192-bit key with the AES encryption algorithm
AES256 - a 256-bit key with the AES encryption algorithm
The ZyWALL and the remote IPSec router must both have at least one
proposal that uses use the same encryption and the same key.
Longer keys are more secure, but require more processing power,
resulting in increased latency and decreased throughput.
Select which hash algorithm to use to authenticate packet data in the
IPSec SA. Choices are SHA1 and MD5. SHA1 is generally considered
stronger than MD5, but it is also slower.
The ZyWALL and the remote IPSec router must both have a proposal
that uses the same authentication algorithm.
This column contains icons to add and remove proposals.
To add a proposal, click the Add icon at the top of the column.
To remove a proposal, click the Remove icon next to the proposal.
The ZyWALL confirms that you want to delete it before doing so.
Select whether or not you want to enable Perfect Forward Secrecy
(PFS) and, if you do, which Diffie-Hellman key group to use for
encryption. Choices are:
none - disable PFS
DH1 - enable PFS and use a 768-bit random number
DH2 - enable PFS and use a 1024-bit random number
DH5 - enable PFS and use a 1536-bit random number
PFS changes the root key that is used to generate encryption keys for
each IPSec SA. The longer the key, the more secure the encryption,
but also the longer it takes to encrypt and decrypt information. Both
routers must use the same DH key group.
The ZyWALL can regularly check the VPN connection to the gateway
you specified to make sure it is still available.
Select this to turn on the VPN connection check.
Chapter 21 IPSec VPN
347