Remember user implementation

Hi
I need to implement a remember user [similar to remember facilty appearing in login screens of most web sites] in an IPhone application. Initially, I tried by first creating a .strings file in Resources folder but it seems to me that we can only read from the file but cannot modify them
If I place the same file outside of my application directory, I am be able to read as well as modify it.
Since the information is very small, hardly 5 lines so i do not want to use any database like sqlite.
But storing such information in text format is critical.
Can it be possible to store it in encrypt format?
If yes, then how?
Does Property list be of any help here?