Chapter 13 VPN
P-79X Series User’s Guide
137
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
Algorithm
Select DES, 3DES or AES 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.
Note: The DES encryption algorithm is not supported at the time of writing.
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
(Seconds)
Define the length of time before an IPSec 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.
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
Algorithm
This field is available when you select ESP in the Active Protocol field.
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.
Note: The DES encryption algorithm is not supported at the time of writing.
Table 49 Security > VPN > Setup > Edit > Advanced Setup (continued)
LABEL DESCRIPTION
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