ZyXEL Communications P-335WT - Manual (Page 233)

P-335 Series User’s Guide
Chapter 17 VPN Screens 233
17.13 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 74 VPN IKE: Advanced
LABEL DESCRIPTION