Step 1: Zip the file/folder to be hidden
#zip xyz.ppt.zip xyz.ppt
Lets assume that abc.jpg is the image we are using for the camouflage.
Step 2: Hide the zipped contents
#cat abc.jpg xyz.ppt.zip > new.jpg
The new.jpg will be jpg file that hides the zipped content. The file will have meta data as jpg and any image viewer will be able to open it.
To extract the hidden contents:
Vola!! Thats it. Its as simple as it is! Thanks to Naveed for this tip.