LÖVE

The site http://mkottman.github.io/luacrypto/manual.html has a library for encrypting strings into MD5 strings.
By serialising files you can compare files on the local storage device with an expected MD5 string to detect if there are any discrepancies (via hacking or cheating, etc.)
This is very handy library and I request it's inclusion into this amazing engine!



Thank you for your time.
- OnlyFails

If they can change the files in the hard drive, they can change the source code (and make md5 return "true").

That said, there're several plain-lua implementations of md5 around. It so happens that I have one:

https://github.com/kikito/md5.lua

Mind you, since it's compatible with Lua 5.1 it doesn't use LuaJIT's bit32 library, so it must use strings for binary ops. So don't expect super-duper fast results. But you should be ok for small or medium things (like textual config files).

Here are a couple more you can use which use LuaJIT's FFI:

https://github.com/Wiladams/LAPHLibs
http://luapower.com/md5

So it took me about over a week to figure out but I'm compiling my own version of love with the obvious issues kikito mentioned.
By compiling my own version I can keep the source code hidden so it can't be modified, to prevent tampering.

Thanks again guys, the forums are amazing filled with helpful people and active developers!