SteganoPNG is a simple tool to steganographically (hidden & secret) encode your file into .PNG image
java -jar SteganoPNG.jar -c source.png yourfile.ext KEY output.png
java -jar SteganoPNG.jar -d stegano.png KEY output.ext
-c - encrypts your file by specified KEY and encode it into .PNG
-d - try to decrypt and extract file from steganographic .PNG
java -jar SteganoPNG.jar -c picture.png hidden_message.txt SecREtKeyPassWord wallpaper.png
java -jar SteganoPNG.jar -d wallpaper.png SecREtKeyPassWord hidden_message.txt