 Hey y'all, Mr. Gibson here, and welcome to the next lesson in cryptography. In this video, we'll be taking a look at the App Bash Cypher, its history, and how to use it to EnCypher in DeCypher messages. The App Bash Cypher is a substitution cypher originally used to encrypt the Hebrew alphabet. The name derives from the first, last, second, and second to last Hebrew letters, elif, ta, bet, and shin. The App Bash Cypher is a particular type of cypher formed by taking the alphabet and mapping it to its reverse so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on. For example, the Latin alphabet that we use would look like this. We can quickly use this mapping between the plain text and cypher text alphabets to create our cypher text. Since this cypher has only one way to perform it, that is there is no key, it's not very secure. Once you know the method, you can read any message that's been encrypted using this cypher. Decyphering the App Bash is the exact same process as encyphering it. The encyphering process will decrypt the message as well. We can say that this operation is its own inverse. That's all there is to the App Bash Cypher. We'll look at this cypher again in a little while once we've learned how to program, and we can realize how we can use mathematics to describe this operation instead of having to line up the two alphabets and follow the path across. That's it for now, and we'll catch you on the next one.