P-661H/HW Series User’s Guide

Table 85 Advanced VPN Policies (continued)

LABEL

DESCRIPTION

 

 

Negotiation Mode

Select Main or Aggressive from the drop-down list box. Multiple SAs connecting

 

through a secure gateway must have the same negotiation mode.

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.

Encryption

Select DES, 3DES or AES from the drop-down list box.

Algorithm

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.

Authentication

Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and

Algorithm

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 SHA1 for maximum security.

SA Life Time

Define the length of time before an IKE SA automatically renegotiates in this field.

(Seconds)

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.

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.

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Chapter 13 VPN Screens