Nonlinear-feedback shift register
Imagine you have a big box full of colorful marbles. You can dump them out, count them, and put them back in the box any way you like. That's kind of like a shift register.
Now imagine you have another box of marbles, but this time they're all black, except for one special yellow marble. You can put in as many black marbles as you want, but the yellow marble always starts at the beginning.
If you count the marbles in the box after each turn, the order of the marbles will change. If you make sure to take out the yellow marble before you count, you can get a sequence of numbers that seem random.
But if you know how many black marbles are in the box, and you know the rules for how they move around, you can predict what the next number in the sequence will be. That's kind of like a linear-feedback shift register.
Now imagine the box of black marbles is twice as long, and there are two yellow marbles that move around independently of each other. That's kind of like a nonlinear-feedback shift register. The order of the marbles is still changing in a way that seems random, but it's much harder to predict what the next number in the sequence will be because there are two "moving parts" instead of just one.
Now imagine you have another box of marbles, but this time they're all black, except for one special yellow marble. You can put in as many black marbles as you want, but the yellow marble always starts at the beginning.
If you count the marbles in the box after each turn, the order of the marbles will change. If you make sure to take out the yellow marble before you count, you can get a sequence of numbers that seem random.
But if you know how many black marbles are in the box, and you know the rules for how they move around, you can predict what the next number in the sequence will be. That's kind of like a linear-feedback shift register.
Now imagine the box of black marbles is twice as long, and there are two yellow marbles that move around independently of each other. That's kind of like a nonlinear-feedback shift register. The order of the marbles is still changing in a way that seems random, but it's much harder to predict what the next number in the sequence will be because there are two "moving parts" instead of just one.