The file encTitleKeys.bin is a database of used by the Nintendo 3DS to authenticate and download software directly from Nintendo's Content Delivery Network (CDN). It essentially acts as a collection of "tickets" or licenses that trick the console into thinking it has the right to download and install specific games. Purpose and Functionality
This is why many discussions about "enctitlekeys.bin top" also reference . The two files work together to decrypt modern 3DS software. enctitlekeysbin 3ds top