ZyXEL Communications Internet Security Gateway ZyWALL 2 Series User Manual page 233

LABEL
Authentication 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
algorithm is generally considered stronger than MD5, but is slower. Select MD5 for
minimal security and SHA-1 for maximum security.
SA Life Time Define the length of time before an IKE SA automatically renegotiates in this field. It may
(seconds) range from 180 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.
Key Group 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.
Phase 2
Active Protocol Use the drop-down list box to choose from ESP or AH.
Encryption This field is available when you select ESP in the Active Protocol field.
Algorithm
Select DES, 3DES, AES or NULL from the drop-down list box.
When you use one of these encryption algorithms for data communications, both the
sending device and the receiving device must use the same secret key, which can be
used to encrypt and decrypt the message or to generate and verify a message
authentication code. 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. This implementation of AES uses a 128-bit key. AES is faster than 3DES.
Select NULL to set up a tunnel without encryption. When you select NULL, you do not
enter an encryption key.
Authentication Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and SHA1
Algorithm (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.
VPN Screens
Table 14-8 Advanced
ZyWALL 2 Series User's Guide
IKE VPN Rule Setup
DESCRIPTION
14-27