[hackarchives]

Just formulate a logic and it will be clear what you have to do.
You'll have to first make an index of shortening URLs, and create a random link. Then via code just put a redirect to whatever link you want.

ALthough of low concern but random url will not be encourage due to chances of collision[minute chances].there should be some sequence or some order in which you can store them..

Or, you can just call the random function you use again if the generated link exists in the database