SpotPass

SpotPass is a Nintendo 3DS feature that allows the 3DS to automatically download content, notifications, and software when it's in standby/active mode. SpotPass can upload content as well. Software downloaded with SpotPass is stored on SD card.

SpotPass Internet communications are mostly small UDP frames and HTTPS transfers, the only HTTP download is the connection test page.

With the 2.0.0-2 update, SpotPass now regularly requests content over HTTPS from nppl.c.app.nintendowifi.net and sometimes nasc.nintendowifi.net. These are probably related to the SpotPass automatic software download functionality. Going by the domain names, nppl* might be for SpotPass software downloads? In System Settings, you can disable SpotPass content downloading,(this is _only_ for free titles etc not auto system updates) but it states that important software will still downloaded. This is likely why SpotPass still connects to nppl* even with that option disabled.

'nasc.nintendowifi.net' confirmed usages:

• Friends List application requires this server to be 'Online' (most likely the reason for regular requests to this server)
• Required for initialization of E-shop, (for first time e-shop users). Not required for using E-Shop after first use.

Homemenu SpotPass usage

Homemenu uses two domains with HTTPS for SpotPass. SpotPass stores this content in Homemenu's NAND shared extdata.

• Via the a248.e.akamai.net cache mirror npdl.c.app.nintendowifi.net is accessed. The content(using the SpotPass content container) downloaded from this seems to be related to notifications possibly. There's 4 files download from here, each of which are downloaded if updated every 24 hours. There's separate files stored on the server for each region and language.
• The pls.c.shop.nintendowifi.net domain is used for uploading data from the NAND shared extdata. "pl" might be referring to "play log"? This is uploaded every 24 hours.

Automatic System Update Download

With the 2.0.0-2 update, system updates updates are automatically downloaded via SpotPass. It only downloads updates, it will not install updates without the user's permission. See this: http://www.nintendo.com/consumer/systems/3ds/en_na/menu_update.jsp

SpotPass downloads/checks for updates every 24 hours. This is identical to the system used for manual system updates: when it's time to check for updates, SpotPass will send a system update SOAP request to the server. When there's an update available, SpotPass will then do the usual sysupdate procedure like manual sysupdates.

Content Container

All SpotPass content uses this container to encrypt the payload.(and possibly sign it) The cleartext payload is stored in extdata.

Offset	Length
0x0	0x4	Magic Number "boss"
0x4	0x4	Always 00 01 00 01
0x8	0x4	Big-endian filesize
0xC	0x4	Always 00 00 00 00
0x10	0x4	Release date (UNIX timestamp)
0x14	0x8	Always 00 01 00 00 00 02 00 02
0x1c	0x27a?	Unknown, going by the size of this a RSA-4096 signature might be stored here among other things?

Data following the header is encrypted, the CTR used is likely based on metadata in the header.(like the timestamp) It appears that this file format is big-endian, unlike other 3DS formats.