problem with alarm

It doesnt happne all the time but when i put the key in to start the ignition sometimes it wont start. Nothing happens and the security light is on and the display in the car says to clean the key and try again in 3 min. After the 3 min. if i try again sometimes it will start sometimes and sometimes not and i have to wait another 3 min. to try again. I dont think its the key because i started using my spare and it happens with that one to. Is there something i can do to fix it?