On live, I believe they encrypted everything (spawns were all unknown and user was level 1). I believe it used to be an 8 bit encryption then they changed it to 32 bit (might have been 64 bit) but for some reason they got rid of it and changed it to an xor. For a long time, there was a libeq.a file, it had all the decryption in it. I believe it is in the libeq.cpp in the versions used by 1999.

I was never very good at the code, I helped occasionally. Structvis used to help me quite a bit. (it is still somewhere on the forums). You will have to take my posts with a grain of salt. It has been MANY years since I really played and even longer since I had done anything with the code.