Wednesday, 5 July 2017

Encryption - Codewords and Lesson 4 PGP


This work refers back to last lesson when you looked at how the frequency that letters appear in our language can be used as a starting point for decrypting a code.

I have provided a worksheet of a total of 6 Codeword puzzles.  Each square on the grid has been given a number and that refers to a letter of the alphabet.  You are provided with 3 letters to start with and, once they have been written into the relevant squares, you have to try and work out what the words could be and therefore what letter the numbers represent.

Have a go!  Use pencil and rubber if you have them!

Hint: Write out the alphabet under the grid to start with and cross off the letters as you work out which numbers they are.  This will give you a record of which letters are still to be used.

PGP - Pretty Good Privacy
For the work for this you need to go to the link below and work through the tasks on the slideshow.....

Evidence all work on your blog or shared Google doc (as appropriate) as usual and publish the post at the end of the lesson.

Friday, 16 June 2017

Encryption - Lesson 3 breaking the code

Encryption - Lesson 3 Breaking the code

This lesson is about how we can start to decipher a coded message using knowledge of words and frequency of letters used.

The presentation on this link .......

explains all the tasks you need to do for this lesson.

I think it's fairly self-explanatory and, therefore, am not writing any specific instructions on this post.

Just read each slide carefully and work through the tasks in sequence.

Don't forget to publish your post at the end of the lesson!

Wednesday, 14 June 2017

Encryption Lesson 2 - Substitution Cipher

Substitution Cipher

Objectives and Outcomes:
  • be able to explain how a substitution cipher works (band 4)
  • be able to apply your understanding by creating your own substitution cipher and encoding a message (band5)

Many realised that the Caesar Cipher was weak; it was too easy to break.  The Substitution Cipher was developed to overcome this weakness.

The Substitution Cipher involved moving different letters of the alphabet around and put into a random position.

Each letter of the alphabet is replaced by another.

Your tasks
1.  On a new blog post, titled the same as this one, explain how a substitution cipher works.

2.  On a Google doc, create your cipher in the same way as I have shown you, but with different randomly placed letters.

3.  Apply your cipher by encoding the phrase 'Computer science rocks'.  Write the message and the code under your cipher table.

4.  Under this, copy my cipher from my blog.

5.  Using my cipher, decode this message: X  RXSP  OEXTXCK  BPIEPT  VPBBDKPB.

6.  Share your Google doc to 'Anyone with the link' and copy/paste the link to your post, under your first piece of writing.

7.  Explain how this cipher is better than the Caesar Cipher.

8.  Explain what senders and recipients of the coded messages would need to be able to encipher and decipher the messages accurately.

9.  How could the messages be further protected against being deciphered if intercepted regularly by others?  Write your detailed answer on your post.


Tuesday, 6 June 2017

Encryption lesson 1 - Caesar Cipher

Encryption lesson 1 - Caesar Cipher

Objectives and Outcomes

  • be able to describe what a cipher is (band 4)
  • be able to create your own cipher algorithm (band 5)

You have been given 2 circles of a Caesar Cipher wheel.  The smaller circle sits on top of the larger one,  if you put a pen-point on the dot in the middle, you should be able to turn the top circle slowly over the bottom one which should stay still.

This cipher wheel was a very early machine used to help enciphering and deciphering secret messages.

It works by matching the "A" on the inner wheel to the appropriate shift letter on the outer wheel (turning clockwise - to the right); so for a shift of 3, "A" would be lined up with "D" on the outer wheel and all the other letters can then be read off.  You can use negative number shifts by going backwards (anti-clockwise - to the left), eg -1 "A" would line up with "Z".

1.  On a new blog post, titled the same as this one, explain what the Caesar Cipher is, how it works and how a cipher wheel can be used to help (do not just copy/paste what I've written!).


3.  Write the code and your deciphered message on your blog, explaining how you worked it out.

4.  Write a message of your own and encipher it using the Wheel.  Write this on your blog.  Get a partner to try and decipher it.

5.  On your post, explain how easy it might be for someone who intercepts a secret message using this cipher to work out the original.

6.  On your post, write ideas of how this system could be adapted to make it harder to work out the coded message.


Wednesday, 3 May 2017

Microbits theory lesson

Microbits theory lesson

You are to spend this lesson improving and extending the work you did on your blog last lesson.  You will need the presentation for Microbits, lesson 1 on the Computer Science section of the school website.

1.  Make sure you have completed the task on slide 4.

2.  Using the link on slide 10 (in 'Present' mode), go to Python and follow the instructions on slide 14. Paste the screenshot to a Google doc. You do not need your microbit to actually run the program.

3.  Go to slide 17 and edit your python code to display a happy image.  Don't forget to add the screenshot to your Google doc, under the previous one.

4.  Go to slide 19 and repeat the above instructions.

5.  Go to this link and read through the 3 pages of information.

6.  Click on the tab that says 'Test'.

7.  Do the test and printscreen you results on your Google doc under your programming screenshots.

8.  Share your Google doc correctly (Advanced - change from Private to 'Anyone with the link).  Copy/paste the link to your blog post.  Update or Publish!

Friday, 24 March 2017

Computer Networks

Your blog work for this lesson!

1. Give a definition of what a computer network is, with an example (use GCSE Bitesize - Computing to help if needed).

2.  Open Google and type in 'what is my IP address?' Screenshot your result to a Google doc.

3.  You've found your computer 'postcode' (IP address).  Use to find the IP address of ''.  Take a screenshot and paste it onto your Google doc under the first one, giving an explanation of what it shows.

4.  Pick ONE website of your choice.  Find it's IP address.  Find it's Registrant details, including when it was first registered.  Write these details, including the website URL on to your blog post.

5.  You've just used a DNS source.  Use Google to find out what DNS stands for and (simply) how it works.  Write it on your post.

6.  Share your Google doc to Anyone with the link and copy/paste it to your post.


Friday, 3 February 2017

Computers in Business - databases

Your tasks for this lesson

This lesson involves researching the answers to the following questions.  Answers to be written on a new blog post titled the same as this one.

1.  What are databases?

2.  Find 2 organisations that use databases and describe how they use them and for what tasks.

3.  Explain how databases are different to spreadsheets and how this determines their use for particular tasks.