Hello,
Unfortunately, the Encrypted Return URL IPN feature is
currently in beta mode and we will soon release the proper
documentation and sample code for you to use it. For the time being, we
would advise against is usage.
Your IPN Security Code, should never be displayed on your website as it is used by your IPN Handler script to authenticate the IPN data that AlertPay sends to you. Only AlertPay and you should know its value.