I have got a response from the AlphaCommerceHub support:
There is the tokenization function as part of the HPP implementation that will cause the system to return a token after a transaction is processed.
This happens automatically when AlphaSecure is included in the process flow for AuthPayment.
http://developer.alphacommercehub.com.au/docs/alphahpp-#tokenization-
This should be used to store the token so that you don’t need to handle the card number directly.