Compatible Systems 5.4 - Manual (Page 107)

Chapter 6 - VPN Ports and LAN-to-LAN Tunnels 101
To add, remove, or edit a Transform, you must access the IKE Configuration
Dialog Box by selecting the Add..., Remove..., or Edit... buttons.
IKE Configuration Dialog Box
Authentication
This set of checkboxes specifies the authentication algorithm to be used for
the negotiation. MD5 is the Message-Digest 5 hash algorithm. SHA is the
Secure Hash Algorithm.
Choosing either of the top two checkboxes means that the Encapsulating
Security Payload (ESP) header will be used to encrypt and authenticate
packets.
Choosing either of the bottom two checkboxes specifies that the Authentica-
tion Header (AH) will be used to authenticate packets.
Encryption
This set of checkboxes specifies the encryption algorithm. DES (Data
Encryption Standard) uses a 56-bit key to scramble the data. 3DES uses three
different keys and three applications of the DES algorithm to scramble the
data.
v Note: You may choose only one authentication and one encryption method.
The default setting of ESP (MD5,DES) is recommended for most setups.