Used by thousands of teachers around the World!

STEP 1

The History of Cryptography

STEP 2

What is Cryptography?

STEP 3

Code or Cipher?

A secret code replaces words, phrases and sentences with groups of numbers or letters


Ciphers use substitutes or rearrange letters.       


OMG  (oh my God) and LOL (Laugh out Loud or Lots of Love) are examples of ciphers


Both codes and ciphers need a key to be able to decipher (work out what they mean)

STEP 4

Code Cracking

To crack a code or cipher you need to know the rules used to make the code.

You need to know the key!

STEP 5

Make your own Secret Messages

Download the secret messages worksheet



Download Worksheet

CHALLENGE (OPTIONAL)

Design your own simple code scrambling algorithm (rule).


Then use Scratch to create a computer program. The user enters the letters of the alphabet and they are replaced with another letter, according to the rules of your algorithm.


Tip: You could use Scratch 'Lists' for this...

for example: position 1=a, position 2=b etc.

Write a cipher program



Go to Scratch