Archive.org (Internet Archive) hosts a vast collection of software preservation files, including:

Archive.org allows users to download entire collections via Torrent or direct ZIP files, making it easy to build a complete "set" for offline storage. How to Find "archive.org 3ds decrypted" Sets

This paper presents an attack on the encryption used by 3DS games. Weinmann discusses how to exploit weaknesses in the encryption scheme to decrypt 3DS game data.