Scratch Advanced – Week 5 – Cracking the Caesar Cipther

This week we began the task of cracking the following codeed message.

XUFHJ YMJ KNSFQ KWTSYNJW. YMJXJ FWJ YMJ ATDFLJX TK YMJ XYFWXMNU JSYJWUWNXJ. NYX HTSYNSZNSL RNXXNTS YT JCUQTWJ XYWFSLJ SJB BTWQIX, YT XJJP TZY SJB QNKJ FSI SJB HNANQNEFYNTSX, YT GTQIQD LT BMJWJ ST TSJ MFX LTSJ GJKTWJ.

All we know is this message is written in English. To crack this code we will use some common features of the English language.

  1. In the coded mesage look for single letter words. These words probably map to a or I
  2. In the coded message look for the most common three letter words. These words are the, and
  3. in the coded message look at the spelling of any other small word to see if we can figure out their original form.

How to crack Ceasar Cipher

The following link was the hand out provided to everyone. Each person used this handout to work through each stage of the decryption.

Can you decrypt this message (pupils notes)

The teachers handouts is available at the following link. This handout provides detailed steps of how to work through decrypting the message.

Can you decrypt this message (teachers notes)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s