SpotPass

SpotPass is a Nintendo 3DS feature that allows the 3DS to automatically download content, notifications, and software when it's in standby mode.(SpotPass may download/upload some content while the 3DS is in "active" mode, but *only* if the currently active app uses SpotPass) 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 sign it. The cleartext payload is stored in extdata. The format of these headers is big-endian.

BOSS Header

Offset	Length
0x0	0x4	Magic Number "boss"
0x4	0x4	Magic Number 0x1000100
0x8	0x4	Big-endian filesize
0xC	0x8	u64 release date (UNIX timestamp)
0x14	0x2	Must always be 0x1
0x16	0x2	Padding
0x18	0x2	Content header hash type, always 0x2 for SHA-256
0x1A	0x2	Content header RSA type, always 0x2 for RSA-2048
0x1C	0xC	First 12 bytes of the CTR

Data following the header is encrypted with AES-CTR. The first 12 bytes of the CTR are from offset 0x1C of the header, while the last word of the CTR in big-endian is 0x1. The cleartext data begins with another header. Following that header is the actual content.

Content Header

Offset	Length
0x0	0x10	?
0x10	0x2	?
0x12	0x20	SHA-256 hash
0x32	0x100	RSA-2048 signature over the above hash

The hash at offset 0x12 hashes the 0x10-byte data at offset 0x0 followed by a zero u16.