As I already said in another topic (yes, the "news" has already been posted, do a search first), it's not the 3DS firmware, it's only the "updated files" downloaded by the 3DS to update the "full" firmware already stored on the console.
It's just multiple "patch" files and has nothing to do with a real Firmware Dump.
These files are copyrigthed the same way as Wii IOS are, they can't be shared, only downloaded by the user directly on Nintendo server. (using NUSD or simple URL in your browser).
Plus, he didn't decrypt anything, the structure is copied (and translated) from 3dbrew.org
Please, don't share links to Nintendo server's file.
Edit:
If it was really a dump :
DS mode firmware would produce ARM7.bin, ARM9.bin + a BIOS file
3DS mode should produce a NAND dump like the wii, as it's using the same update process.
And as every 3DS have a different firmware (different keys), you can't use another user dumped firmware, you would need to run the dumping tools yourself. (in form of a homebrew or a hardware reader)