ZyXEL ZyWALL 5 User Guide - Page 100

Chapter 4 Wizard Setup The following table describes the labels in this screen. Table 19 VPN Wizard: IKE Tunnel Setting LABEL DESCRIPTION Negotiation Mode Select Main Mode for identity protection. Select Aggressive Mode to allow more incoming connections from dynamic IP addresses to use separate passwords. Encryption Algorithm Authentication Algorithm Key Group SA Life Time (Seconds) Pre-Shared Key Back Next Note: Multiple SAs (security associations) connecting through a secure gateway must have the same negotiation mode. 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. 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. 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 (1 Kb) random number. DH5 refers to Diffie-Hellman Group 5 a 1536-bit random number. 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. Type your pre-shared key in this field. A pre-shared key identifies a communicating party during a phase 1 IKE negotiation. It is called "pre-shared" because you have to share it with another party before you can communicate with them over a secure connection. Type from 8 to 31 case-sensitive ASCII characters or from 16 to 62 hexadecimal ("0-9", "A-F") characters. You must precede a hexadecimal key with a "0x (zero x), which is not counted as part of the 16 to 62 character range for the key. For example, in "0x0123456789ABCDEF", 0x denotes that the key is hexadecimal and 0123456789ABCDEF is the key itself. Both ends of the VPN tunnel must use the same pre-shared key. You will receive a PYLD_MALFORMED (payload malformed) packet if the same preshared key is not used on both ends. Click Back to return to the previous screen. Click Next to continue. 4.6 VPN Wizard IPSec Setting (IKE Phase 2) Use this screen to specify the authentication, encryption and other settings needed to negotiate a phase 2 IPSec SA. 100 ZyWALL 5/35/70 Series User's Guide