Leftover hash lemma

The Leftover Hash Lemma is a way to prove that a particular computer algorithm is secure, or that it will work in all cases. It says that if you have a list of numbers, and run the algorithm on them, the resulting list will be the same no matter what order the numbers were given in. That means that if someone tries to mess up the algorithm by changing the order of the numbers given, the result will still be the same. This helps prove that the algorithm is secure, and will always work as expected.