NWM Services

These NWM services are used for local-WLAN communications, NWM module handles regular wifi APs as well. These services are used for creating/connecting to networks, and for sending/receiving data over the network etc. NWM module uses the wifi SDIO hardware via the IO registers for this.

Local-WLAN

UDS is used for 3DS<>3DS local-WLAN communications, and for 3DS<>Wii U communications. The latter is mainly only used for multi-player in games.

All UDS local-WLAN communications have the CCMP key for data encryption generated via NWM module. The CCMP key passed to nwm::CEC commands(stored in a 0x44-byte input structure) for StreetPass is generated by the CECD module. The input data used with EncryptDecryptAes with keytype1 is a MD5 hash over an input passphrase. This input passphrase is fixed for Download Play, it's unique per local-WLAN protocol. The CTR is a MD5 hash over the below 0x10-byte structure. The output from encrypting that data with AES-CTR is the final CCMP key.

Structure used for generating the CTR

Offset	Size	Description
0x0	0x4	Little-endian local-WLAN communication ID, normally this is the user process' UniqueID from the titleID. For Download Play, this is always 0x2810 on retail.
0x4	0x4	Little-endian u32 networkID, randomly-generated when creating the network. The network SSID used when a client connects to the network is sprintf(out, "%08X", networkID).
0x8	0x6	Host MAC address.
0xE	0x2	Little-endian ID, for Download Play this is 0x55.

UDS Beacons

The UDS host broadcasts a beacon containing at least two Nintendo-vendor tags. The second tag contains the big-endian u32 networkID, used by the clients when connecting to the host and for the above CCMP key generation. The Nintendo-vendor tag(s) following the first two are unique to the process using UDS, these tags are used for broadcasting metadata regarding the host, like the host 3DS nickname, icon data for Download Play, etc.