[FONT="]While block ciphers make sense without much trouble, I am having trouble with stream ciphers. How is it done? Do they require each bit to be encrypted individually? If so, how is this done without requiring a very large amount of processing overhead? Why is repeating a key create a vulnerability more with stream ciphers than with block ciphers which is how I understand it? Are the keys repeated in a pattern that can be detected which isn't done with the other?