f6a461ee_IPsec_VPN___UntangleWiki__Description
[Name] Shared Secret [Description] 
This field should contain the shared secret or PSK (pre-shared key) that is used to authenticate the connection, and must be the same on both sides of the tunnel for the connection to be successful. Because the PSK is actually used as the encryption key for the session, using long strings of a random nature will provide the highest level of security.
IPsec VPN - UntangleWiki
Description