SQL Server 2008 :: Does Change Data Capture Require A Table Have Primary Key

Or can it record before and after column changes based on the LSN only?

An extract from a file based legacy accounting system is performed every night. The system does not have a primary key because transactions are managed through program code. (the more things change...). The extract is copied to text in Unix and FTP'd to Windows, where the file is loaded into SQL Server by kill & fill. Because of the expense of modifying the source system, there is enormous inertia/resistance to injecting a primary key at the source, so kill & fill it stays.

In reading about Change Data Capture, it seemed to me that column level insert update and delete are stored in tables that remember the before and after content of each column tracked. In my reading I have seen many references to the LSN to decide when and what to record as changed, but I have not seen any refereference to the necessity of a primary key for Change Data Capture to work. This is in contrast to replication, where the requirement for the existence of a primary key is made plain.

Is it possible to use Change Data Capture against a table without a primary key? How to use it to change the extract from kill and fill to incremental.