Bandai Namco doesn’t officially support decryption or DLC redistribution. The 3DS eShop is closed, but the IP remains active. If you truly love Aikatsu Stars!, consider supporting official merchandise or the arcade game. That said, game preservation is important—decrypt your own files, keep backups, and don’t redistribute full DLC packs publicly.
The 4th Anniversary "Starlight Infinity" Dressia
The decrypted DLC often unlocks "Event Coords" that were distributed via local wireless in Japan or via serial codes (which are now expired).