 Hey all, Mr. Gibson here and welcome to the next lesson in cryptography. In this video, we'll be taking a look at the route cipher and how to use it to encipher and decipher messages by hand. The route cipher is another type of transposition cipher, similar to the rail fence cipher. However, unlike the rail fence, there's a little bit more flexibility in how you create the cipher text. We'll use our plain text message, arose by any other name, which has 19 characters, and start by selecting a grid that can hold all 19 characters. In this case, you've chosen four rows and five columns. If you can't get a grid to nicely fit your message, like ours, you can always add junk characters like the letter X to fill it out, since the person deciphering the message will know they're just filler. You start by writing your plain text message, column by column, working from left to right. For our message, we would start with the letter A in the top left, and then moving down R, O, S, up to the top of the next column, E, E, and so on. When you get to the end, you can put an X to fill out the grid. Now, to create the cipher text, we'll use the key. In this case, the key is a written description that tells you how to move through the grid to collect your letters to form the cipher text. This key reads spiral inwards, clockwise, starting from the top right. So starting in the top right box, whether it's the letter A, we'll move inwards, clockwise, through our characters to figure out the cipher text message. It should give us A, M, E, X, N, and so on. And now we have our cipher text message. You can see, again, this is another transposition cipher. For none of the letters have changed just their positions. To decipher using this system, we're going to start by spiraling using the key, and then we'll create the plain text by reading it off column by column left, right. So our key here says spiral inwards, clockwise, starting from the bottom right. So the letter E will go on the bottom right, and we'll move clockwise, filling in the letters one by one. Once we fill the grid, we can move left to right and realize that our plain text message is half blood rinse from Harry Potter. And that's it. You should now be able to decipher and decipher messages using the route cipher. Thanks for watching, and we'll catch you in the next one.