and anybody can take my code??
Is there anything which evaporates the code so that even the developer cant get back the code again once its uploaded on the arduino.
What if the main supply is cutoff before opening the box??
What if the main supply is cutoff before opening the box?? The arduino wont be able to load new sketch from the SD card.
The only thing which i wants to safe is my code
I would suggest that you use the lock bits.
They do not guarantee that the code is unreadable. A high voltage programmer can change the lock bits back.
I hear that there are still "overseas entities" that will provide the code given a "protected" chip and some "moderate" amount of money. ($100<x<$10000 ?)) (Or maybe they just take your money...)
Thermite and a starter which does not require a battery?