In order to set the formatting to sha1 you will need to update the insert server behavior that is on the registration page. You will need to replace it with a DataAssist insert so that you can apply the formatting to the binding. This is shown in the following Solution Recipe video for modifying the registration page:
04_registration.swf
You should also take a look at the other parts of the Solution Recipes and documentation that is available on the support page:
securityassist/