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.

NWM local-WLAN service "nwm::UDS"

Command Header	Available since system version	Description
0x00030000		Shutdown
0x000F0404		RecvBeaconBroadcastData
0x00100042		SetBeaconAdditionalData
0x001400C0		RecvBroadcastDataFrame
0x001B0302		Initialize
0x001D0044		BeginHostingNetwork
0x001E0084		ConnectToNetwork
0x001F0006	Unknown, >2.0.0-2	DecryptBeaconData

NWM infrastructure service "nwm::INF"

Command Header	Description
0x000603C4	RecvBeaconBroadcastData
0x00070742	ConnectToAP

NWM local-WLAN StreetPass service "nwm::CEC"

Command Header	Description
0x000D0082	SendProbeRequest

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 for CCMP key generation

Offset	Size	Description
0x0	0x4	Local-WLAN communication ID, normally this is: (user_process uniqueID << 8) | val. Where val is 0x10 on retail(configmem UNITINFO bit0 set), 0x90 for devunit. For Download Play, this is always 0x2810 on retail(0x2890 on devunit).
0x4	0x4	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	ID, for Download Play this is 0x55.

This data is stored as little-endian.

CTR used for beacon tags crypto

Offset	Size	Description
0x0	0x6	Host MAC address
0x6	0x4	wlancommID
0xA	0x1	This ID is also stored at offset 0xE in the CTR-generation structure.
0xB	0x1	Padding, value zero.
0xC	0x4	This is the u32 from offset 0x18 in the network-struct.

This data is stored as little-endian. All data here is all-zero except for the MAC address, when the u8 at offset 0x8 in the network-struct is 0.

Network structure

Offset	Size	Description
0x0	0x6	This is the MAC address of the host. This is all-zero on the host, like with NWMUDS:BeginHostingNetwork.
0x8	0x1	This is non-zero when at least one entry is stored in the array under the encrypted beacon data.
0xC	0x3	This is the OUI value for use with the beacon tags. Normally this is 001F32.
0xF	0x1	OUI type (21/0x15)
0x10	0x4	wlancommID
0x14	0x1	This ID is also stored at offset 0xE in the CTR-generation structure.
0x1C	0x1	?
0x1D	0x1	This is the total number of entries stored under the array in the encrypted beacon data.
0x1E	0x1	?
0x1F	0x1	?
0x3F	0x1	Size of additional data. Normally zero.
0x40	0xC8	Additional data, if any. Size of the additional data is specified via the u8 at offset 0x3F. This data is not used when the size-field is zero.

This 0x108-byte structure is used for NWMUDS:BeginHostingNetwork, NWMUDS:ConnectToNetwork, etc. This data is stored as big-endian.

UDS Beacons

The UDS host broadcasts a beacon containing at least two Nintendo-vendor tags(tag number 0xDD, see above for the OUI), normally the data stored in these tags are static. 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.

A tool for these beacons is available here: [1]

UDS Beacon Tags

The following is the structure of each tag, starting at the OUI. The order of the tags is the same as listed below. All data stored under these tags are stored as big-endian.

OUI Type 20

Offset	Size	Description
0x0	0x3	OUI, see above.
0x3	0x1	OUI type (20/0x14)
0x4	0x3	Sample data: 0a 00 00

Normally the size of this tag(from the tag size field) is 0x07.

OUI Type 21

Offset	Size	Description
0x0	0x1F	This is the network structure starting at offset 0xC, with the first 0x1F-bytes from there.
0x1F	0x14	SHA1 hash. When doing the hashing, this hash is cleared to zero. The hash data starts at offset 0x0(OUI), and the size is 0x34 + <value of the u8 at offset 0x33>.
0x33	0x1	Size of additional data. Normally zero. When non-zero this additional data is located at offset 0x34.

Normally the size of this tag(from the tag size field) is 0x34.

OUI Type 24

Offset	Size	Description
0x0	0x3	OUI, see above.
0x3	0x1	OUI type (24/0x18)
0x4	See below	Encrypted data

This is the tag0 used with NWMUDS:DecryptBeaconData. The size of data stored under this tag has a maximum size of 0xFA-bytes, however normally the size is smaller than that. Additional encrypted data, if any, is stored under the below tag1.

OUI Type 25

Offset	Size	Description
0x0	0x3	OUI, see above.
0x3	0x1	OUI type (25/0x19)
0x4	See above	Encrypted data

When this exists in the beacon, this is the tag1 used with NWMUDS:DecryptBeaconData. The data stored here is the 0xFA-bytes following the previous encrypted data in tag0, for more space for storing the encrypted data.

Encrypted beacon data

The following structure is for the plaintext version of the encrypted data.

This data is encrypted with AES-CTR, by NWM module in software. The AES key is stored in NWM module itself. See above for the CTR. The size of this encrypted data is 0x12 + (0x1E*val), where val is the u8 from networkstruct offset 0x1D(zero when the u8 at networkstruct offset 0x8 is value zero).

Structure

Offset	Size	Description
0x0	0x10	MD5 over the rest of the data following this(plaintext).
0x10	0x2	?
0x12	0x1E * <total array entries>	This is an array of entries for each of the devices on this network, the first entry is for the host and the rest is for the client(s).

Array entry

Offset	Size	Description
0x0	0x18	This is the first 0x18-bytes of the structure from here.
0x18	0x4	?
0x1C	0x2	?