https://github.com/PocketMine/PocketMine-MP/blob/mcpe-0.12/src/pocketmine/Player.php#L1841 https://github.com/PocketMine/Pocke...cketmine/network/protocol/LoginPacket.php#L53 Therefore, a string. According to @shoghicp, it is a string created by hash of the combination of server address, server port, client ID and client device ID. Since it is dependent on the server address, the client has different secrets on different servers, and since the device ID is secret, other servers do not know what the client secret is, and since hash is technically considered as an irreversible process, this means that you can use it to identify a unique player (but the player can still change it through a mod, changing client ID or simply registering another DNS that points to your server!) for authentication (but not for banning! Everything from the client is NOT reliable except client IP!).
