ZyXEL Communications ZyWALL 10W User Manual page 248

ZyWALL Series Internet Security Gateway
LABEL
Key Group
Phase 2
Active Protocol
Encryption
Algorithm
Authentication
Algorithm
SA Life Time
(seconds)
Encapsulation
Perfect Forward
Secrecy (PFS)
Apply
Cancel
15-24
Table 15-8 VPN IKE: Advanced
You must choose a key group for phase 1 IKE setup. DH1 (default) refers to Diffie-
Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group 2 a
1024 bit (1Kb) random number.
Use the drop-down list box to choose from ESP or AH.
Select DES, 3DES, AES or NULL from the drop-down list box.
The ZyWALL and the remote IPSec router generate an encryption key from the
Diffie-Hellman key exchange. The DES encryption algorithm uses a 56-bit key. Triple
DES (3DES) is a variation on DES that uses a 168-bit key. As a result, 3DES is more
secure than DES. It also requires more processing power, resulting in increased
latency and decreased throughput. AES uses a 128-bit key. AES is faster than 3DES
and provides a similar level of security.
Select NULL to set up a tunnel without encryption. When you select NULL, you do
not enter an encryption key.
Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and
SHA1 (Secure Hash Algorithm) are hash algorithms used to authenticate packet
data. The SHA1 algorithm is generally considered stronger than MD5, but is slower.
Select MD5 for minimal security and SHA-1 for maximum security.
Define the length of time before an IKE SA automatically renegotiates in this field. It
may range from 60 to 3,000,000 seconds (almost 35 days).
A short SA Life Time increases security by forcing the two VPN gateways to update
the encryption and authentication keys. However, every time the VPN tunnel
renegotiates, all users accessing remote resources are temporarily disconnected.
Select Tunnel mode or Transport mode from the drop-down list box.
Perfect Forward Secrecy (PFS) is disabled (NONE) by default in phase 2 IPSec SA
setup. This allows faster IPSec setup, but is not so secure. Choose DH1 or DH2 from
the drop-down list box to enable PFS. DH1 refers to Diffie-Hellman Group 1 a 768 bit
random number. DH2 refers to Diffie-Hellman Group 2 a 1024 bit (1Kb) random
number (more secure, yet slower).
Click Apply to save your changes back to the ZyWALL and return to the Configure-
IKE screen.
Click Cancel to return to the Configure-IKE screen without saving your changes.
DESCRIPTION
VPN Screens