What is Cryptography?

... and it's got nothing to do with places you bury dead people!!!
We had many, many frustrations with technology this afternoon, but were able to get onto the Khan Academy site and watch a couple of fascinating videos about the Caesar Code and the Polyalphabetic Code. H'mmm... my brain was hurting after using just these two Ciphers... I wonder how the code breakers in World War II felt after a day at work?
The Caesar Cipher https://www.khanacademy.org/math/applied-math/cryptography/crypt/v/caesar-cipher
The Polyalphabetic Cipher
https://www.khanacademy.org/math/applied-math/cryptography/crypt/v/polyalphabetic-cipher

There are many more videos in these lessons on Cryptography, and also some practical activities for trying them out. Hopefully next session we will be able to access a few more of them.
By the time we had used both the ciphers to put a couple of simple words into code, the afternoon had DISAPPEARED!