Typically, Minecraft servers in "online mode" verify every connecting player against Mojang's authentication servers to ensure they own the game. EasyMC bypasses this by utilizing the "EasyMC Auth Server," which acts as a proxy, allowing users to generate "alt tokens" or accounts to join servers that would otherwise require authentication.
However, if you're looking for in areas that apply to or include EasyMC-like clients (game cheating, automation, reverse engineering, or bot detection), here are several good papers and topics you could explore: easymc client