Alice uses the list of random shifts instead.

This is equivalent to having a list of shifts 17,576 numbers long.

Two sets are close to each other in the Hausdorff distance if every element of either set is close to some element of the other set.

Bob decrypts the message by subtracting the shifts according to the secret word he also has a copy of.

Just let the ledge do that, and it's easy, and the next thing you know, there's 20 more tricks based out of the variations.

Then, she sends it to Bob, who decrypts the message using the same list of random shifts she'd given him.

To improve the energy transfer the beams are sent though the main amplifier section four times, using an optical switch located in a mirrored cavity.

Imagine Alice rolled a 26 sided dice to generate a long list of random shifts, and share this with Bob, instead of a code word.

One, the shifts never fall into a repetitive pattern and Two, the encrypted message will have a uniform frequency distribution. because there's no frequency differential, and therefore no leak, it's now impossible for Eve to break the encryption.

So the goal was to produce identical machines that output a scrambled sequence of shifts, which took a long time to repeat.