I play the game Everquest on an officially sanctioned private emulated server. The game was originally released in 1999. It is an MMORPG.
There is an open-source project called 'ShowEQ' that intercepts packets sent to/from the game server, and using those packets, will show additional information about the game (such as locations of enemies on a map, etc) that is not available in the game normally.
The ShowEQ program works without issue on the current official game servers hosted by Daybreak Games, however the makers of the 3rd party emulated server that I play on have added additional packet encryption (Null-Preserving, rotating XOR) which it makes the ShowEQ program slightly more difficult to use successfully. The decryption key is a 10 byte hex key which is sent to the client from the server upon server connection, and can then be used to 'decrypt' packet information allowing a user to successfully use the ShowEQ program.
The article (linked below, especially part 4 of the article) gives vague details on how to get around this, however to an average person like me, it is too difficult. The author of the article claims it can be accomplished in about 30 lines of code.
[login to view URL]@Packet99/installing-showeq-in-2018-81566001ec89
For this project, you will work with the ShowEQ source files to use the 10 byte hex key sent by the game server to apply XOR decryption on packet information, so that it can be displayed in plain text instead of encrypted, garbled information.