Prestige 334 User’s Guide
Chapter 15 VPN Screens
174
15.13 Manual Key Setup
Manual key management is useful if you have problems with
IKE
key management.
IPSec Protocol
Select
ESP
or
AH
from the drop-down list box. The Prestige's IPSec Protocol
should be identical to the secure remote gateway. The ESP (Encapsulation
Security Payload) protocol (RFC 2406) provides encryption as well as the
authentication offered by AH. If you select
ESP
here, you must select options
from the Encryption Algorithm and Authentication Algorithm fields (described
below). The AH protocol (Authentication Header Protocol) (RFC 2402) was
designed for integrity, authentication, sequence integrity (replay resistance),
and non-repudiation but not for confidentiality, for which the ESP was
designed. If you select
AH
here, you must select options from the
Authentication Algorithm
field.
Encryption Algorithm
The encryption algorithm for the Prestige and the secure remote gateway
should be identical. 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. 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.
Authentication
Algorithm
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 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 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.
Perfect Forward
Secrecy (PFS)
Perfect Forward Secrecy (PFS) is disabled (None) by default in phase 2 IPSec
SA setup. This allows faster IPSec setup, but is not so secure. Choose from
DH1
or
DH2
to enable PFS.
DH1
refers to Diffie-Hellman Group 1, a 768 bit
random number.
DH2
refers to Diffie-Hellman Group 2, a 1024 bit (1Kb)
random number (more secure, yet slower).
Basic
Select
Basic
to go to the previous VPN configuration screen.
Apply
Click
Apply
to save your changes.
Reset
Click
Reset
to begin configuring this screen afresh.
Table 52
VPN IKE: Advanced
LABEL
DESCRIPTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
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