ZyXEL Communications ADSL 2+ Security Gateway, User Manual, Page: 83 / 686

Chapter 3 Wizard Setup
ZyWALL 2 Plus User’s Guide
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The following table describes the labels in this screen.
3.6 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.
Table 17 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.
Note: Multiple SAs (security associations) 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.
Pre-Shared Key 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 pre-
shared key is not used on both ends.
Back Click Back to return to the previous screen.
Next Click Next to continue.