Migrate Private Documents from Discussion Type Domino application

We have a requirement to migrate Domino applications to SharePoint. All of the applications are based on a modified Domino discussion template.

One of the modifications is around security and private documents. There are documents that are private to users and upon migration to SharePoint and this needs to be maintained.

So my questions are:

1. How can the migration tool "read" these private documents?

2. How can this privacy be maintained once the documents have been migrated?

Any help would be greatly appreciated.