GTS protocol

The following is wild conjecture based on LordLandon's sendpkm.py.

Communication with the GTS is done over regular HTTP with http://gamestats2.gs.nintendowifi.net/. The same protocol is used for all five Gen IV games.

HTTP headers

The games don't seem to care about these at all. The GTS sends back a bunch of boilerplate response headers, but the game happily accepts a response with only a Content-Length.

Protocol

All requests to the server are GET requests of the form page.asp?pid=pid&hash=hash&data=data. However devices prior to the DSi also send requests without the hash (followed by a requests with hash) to which you should also return proper values or else the DS will assume communication broke off.

pid

The pid is an unsigned 32-bit integer that appears to uniquely identify a game cartridge. Although this has not been confirmed entirely: Your PID is generated when you get your friendcode for the first time and is set to: friendcode & 0x7fffffff When you change the device and are forced to change your friendcode with it, your PID doesn't change but you get a new friendcode (at this point there's no friendcode->pid mapping anymore).

For the mathematically inclined: Eevee's Platinum pid is 192615460 (0x0b7b1424) and his Pal Pad code is 0904 2026 4621.

Challenge/response

(4th Gen)

Before each "real" request, the game sends a request of the form page.asp?pid=pid and the server responds with a 32-byte challenge token. The game computes sha1("sAdeqWo3voLeC5r16DYv" + token) and uses that as the hash value which it sends to the server. The data parameter is encrypted, as explained further down.

(5th gen)

The process is mostly the same, except that the response hash is sha1("HZEdGCzcGGLvguqUEKQN" + token)

That is, each request looks like the following:

1. Game requests GET /pokemondpds/page.asp?pid=pid
2. Server responds with token
3. Game requests GET /pokemondpds/page.asp?pid=pid&hash=sha1(...)&data=data
4. Server responds with payload

The exact details of the game's requests are not currently known, but we are working on it!

Checksum

A 32-bit checksum of the data is used as the key for the encryption. The checksum is simply the sum of every byte of the data.

The first 4 bytes of the sent data are the checksum, xored with 0x4a3b2c1d, and sent in network byte order (big-endian).

Encryption

The data sent to the server is encrypted with a stream cipher, and urlsafe-base64-encoded.

This encryption algorithm, like others used in the game, uses a Linear Congruential Generator (not a very strong choice). The multiplicative constant is 0x45, and the additive constant is 0x1111. It appears that the game uses a signed dword to store the seed, which doesn't really matter; it shouldn't affect anything. (It means that the modulus is effectively 0x80000000.)

GRNG[n+1] = (GRNG[n] * 0x45 + 0x1111) & 0x7fffffff

The GRNG is seeded with the checksum, like so:

GRNG[0] = checksum | (checksum << 16)

The keystream is composed of the lower byte of the high word of successive GRNG values.

keystream[n] = (GRNG[n] >> 16) & 0xff

Xor the keystream with the plaintext to get the ciphertext. Xor the keystream with the ciphertext to get the plaintext.

Conversation

The first request the game makes is to /pokemondpds/worldexchange/info.asp. The server responds with 0x0001.

Platinum, Heart Gold, and Soul Silver will then make a request to /pokemondpds/common/setProfile.asp. The server responds with eight NULs (0x00000000 0x00000000).

After the above step(s) or performing any of the tasks below other than searching, the game makes a request to /pokemondpds/worldexchange/result.asp. If the game has had a Pokémon sent to it via a trade, the server responds with the entire encrypted Pokémon save struct. Otherwise, if there is a Pokémon deposited in the GTS, it responds with 0x0004; if not, it responds with 0x0005.

Receiving a traded Pokémon

If the game receives a Pokémon from a successful trade as a response from result.asp, it next requests /pokemondpds/worldexchange/delete.asp. The server responds with 0x0001.

A note on sendpkm.py

After doing the above, some Platinum, Heart Gold, and Soul Silver games will report a communication error and dump the player back to the title screen. The Pokémon is still successfully received. At least one person with HG/SS has received a Pokémon from a fake server without getting the error, and Diamond/Pearl have never been reported to have the problem.

Depositing a Pokémon

Pokémon are offered on the GTS by requesting /pokemondpds/worldexchange/post.asp. The sent data is 300 bytes long, and includes the Pokémon struct. If the Pokémon is rejected by the server, the response is 0x000c; otherwise, if the deposit is successful, 0x0001.

The game then saves. After the save is complete, it issues a request to /pokemondpds/worldexchange/post_finish.asp.

Retrieving the deposited Pokémon

Checking on the deposited Pokémon is apparently done by /pokemondpds/worldexchange/get.asp. The response appears to be a Pokémon save struct.

Retrieving the deposited Pokémon is done by /pokemondpds/worldexchange/return.asp. The response is merely 0x0001; the actual Pokémon data is taken from the get.asp request.

Searching

Searching is done through /pokemondpds/worldexchange/search.asp. The sent data is either 15 or 16 bytes long.

The server responds with a full 292-byte Pokémon struct for each result. If there are n results, the response will be 292 * n bytes long. If there are no results, the server will give an empty response (0 bytes).

Pokémon struct

The Pokémon data for the Generation IV GTS is 292 bytes—56 bytes larger than a party Pokémon struct. The extra 56 bytes are GTS-specific data, such as the player's name & country, and what Pokémon they are requesting.

They are as follows:

0x00-0x01 Current Pokémon
0x02      Gender          1=male; 2=female; 3=either/neither
0x03      Level
0x04-0x05 Requested Pokémon
0x06      Gender
0x07      Min level
0x08      Max level
0x09      always 0?
0x0A      Trainer Gender  0=male; 1=female
0x0B      always 0?
0x0C-0x13 Timestamp - Deposited time
0x14-0x1B Timestamp - Time traded away?
0x1c-0x1F pid - also 0x4c in the sav
0x20-0x2F Trainer Name
0x30-0x31 Trainer ID
0x32      Country
0x33      City
0x34      Trainer Sprite
0x35      Exchanged flag
0x36      Version         0x0A=Diamond; 0x0B=Pearl; ...
0x37      Language        1=jp; 2=en; 3=fr; ...

The timestamps are set by the server, and are always PST (UTC-8). Timestamp format:

0x00-0x01 Year
0x02      Month
0x03      Day
0x04      Hour
0x05      Minute
0x06      Second
0x07      always 0?

The data for the Generation V GTS is 296 bytes and adds the trainer's secret ID, an additional two unknown bytes at the end, and shifts the position of the trainer name to after the trainer and secret IDs.

0x00-0x01 Current Pokémon
0x02      Gender          1=male; 2=female; 3=either/neither
0x03      Level
0x04-0x05 Requested Pokémon
0x06      Gender
0x07      Min level
0x08      Max level
0x09      always 0?
0x0A      Trainer Gender  0=male; 1=female
0x0B      always 0?
0x0C-0x13 Timestamp - Deposited time
0x14-0x1B Timestamp - Time traded away?
0x1c-0x1F pid - also 0x4c in the sav
0x20-0x21 Trainer ID
0x22-0x23 Trainer Secret ID
0x24-0x33 Trainer Name
0x34      Country
0x35      City
0x36      Trainer Sprite
0x37      Exchanged flag
0x38      Version         0x0A=Diamond; 0x0B=Pearl; ...
0x39      Language        1=jp; 2=en; 3=fr; ...
0x3A-0x3B unknown