HI every one ! i hope u ar having a nice weekend ; )
I got a problem with my project cuz i´m making a security project and that means that a have some important password on my arduino , in the code.
So i have this problem to solve.
How can i avoid that if i lose the arduino and someone finds it , he/she could read all the data from it ?
If u connect the arduino to a pc , is there a way to extract the code from the chip ?
And any idea or suggest that you have to make my project more secure would be awesome !
Thx 2 all 
any idea or suggest that you have to make my project more secure would be awesome
Don't save the password as plain text. Encrypt it in some way for that it is not visible as text in the program. It would still be possible to copy the compiled code from the Arduino and work out what it does but the effort needed to do this would be very large. Would anyone bother ?
After saving your code/data into Flash and EEPROM, you can lock the security bits in order to prevent others from reading your code/data.
The Arduino won’t be the weakest link.
Don’t get too paranoid in your life.
I'm inclined to @larryd's view.
You could have a few arrays in your program that each contain a selection of numbers some of which are ASCII characters but the order of the numbers and which array has which numbers has nothing to do with the text of your password. Then you could have some code in your program that builds the password from a selection of the numbers in the arrays. The actual password would never appear in the source code nor as a string of text in the program - it would only exist while the program is running.
...R
If you store the password, or an encrypted hash value in EEPROM using a separate program, it will not appear in the code.
We used to hide passwords from a casual observer by swapping the nibbles for each byte.
Paul