#fullmetalpixel

Today, I are going to talk about FMP's save system. Traditionally, game save systems are pretty boring. You take some data (usually letters or numbers), and encrypt it so that it cannot be messed with. Then, you save it to a file that can be read by your game, and used to figure out where you were when you saved. Over time, these types of systems have become more complex to prevent players from cheating, but in the process, it has made sharing or backing up your saved game almost impossible.

For our save system, we wanted to do something a little more fun. We are going to use a method called Steganography to save the data. Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message, a form of security through obscurity. 

In simple terms, I am going to save your game data inside the image of your saved game. In more complex terms, I convert a string to bits, and adjust the alpha channel of a few image pixels slightly to represent the bits. Because I know how the pixels are adjusted, I look for those pixels. The first 32 pixels of the image tell me how long my string of saved data is, so I don't have to scan the entire image to find what I am looking for.

Because we store the data this way, it's almost impossible to tamper with your data. If you open the image in an editing program, and adjust just one of the pixels incorrectly, the saved data is no longer readable. However, we are not going to hide these images from you. It's your saved game, and you can do what you want with it. Email it to a friend, embed it into your website, or just back it up for safe keeping. None of these things will affect your saved game, and will allow others to load it quickly and easily.