ZyXEL Communications ZyXEL ZyWALL 5 - Manual (Page 79)

ZyWALL 5 User’s Guide
78 Chapter 3 Wizard Setup
3.3.2 IKE Tunnel Setting (IKE Phase 1)
Figure 18 VPN Wizard : IKE Tunnel Setting
The following table describes the labels in this screen.
Table 14 VPN Wizard : IKE Tunnel Setting
LABEL DESCRIPTION
Negotiation Mode Use the radio buttons to select Main Mode or Aggressive Mode. Multiple SAs
connecting through a secure gateway must have the same negotiation mode.
Encryption Algorithm When DES is used for data communications, both sender and receiver must
know 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.
Authentication
Algorithm
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.
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.
SA Life Time
(Seconds)
Define the length of time before an IKE SA automatically renegotiates in this
field. The minimum value is 180 seconds.
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.