MATHS, NUMBERS
7–11
30 MIN
MAKING OBSERVATIONS • PROBLEM SOLVING • CURIOSITY
MAKING
Skills used
Age
Topic
sciencemuseumgroup.org.uk/resources
Using the cipher wheel to encrypt a message (make it secret)
involves transforming each letter of the message into another
letter or a number by following a series of steps: an algorithm.
Inthis case, the algorithm involves simply shifting each letter
ofthe message by a certain number of places through the
alphabet. Algorithms are commonplace in mathematics. The
message’s receiver is aware of the algorithm – which, in the
caseof cryptography, is called a cipher – and can decrypt
themessages by applying the algorithm in reverse. To
anyoneelse, the message looks nonsensical.
During (and before) the Second
World War, German military
forces used sophisticated
devices called Enigma cipher
machines to encrypt messages.
What’s the maths?
A cipher is a code used to protect information that is being stored or
communicated, so that only people who are allowed can access it. This
activity involves making a cipher wheel and using it to encrypt and decrypt
messages, with a simple cipher.
Overview for adults
Sophisticated encryption is used to send information across
theinternet, ensuring that credit card details, emails and other
messages cannot be read by anyone who intercepts the data.
Many websites are also secured using cryptography, so that
hackers cannot gain access to the computer files that make
upthe website or personal data stored in them. The addresses
ofsecure websites begin with ‘https’ rather than ‘http’.
Maths in
your world
Explore more
The word ‘cryptography’ comes from the Greek words kryptos
(meaning ‘hidden’) and graphia (meaning ‘writing’).
Did you know...?
sciencemuseumgroup.org.uk/resources
Pencil for making
notes and writing
messages
Scissors
Split pin
Cipher Wheel
templates
Make a cipher wheel, and use it to
send secret messages to your friends
and family.
Investigate…
• Could you work out the encrypted message
without the cipher wheel?
• What kinds of things might people want to
keepsecret?
• How quickly can you encrypt and decrypt
amessage?
• Can you use a different cipher (for example
A= 1 X 2 +1, B = 2 x 2 + 1 and C = 3 x 2 + 1)
which is more difficult to solve? Try encrypting
your message and see if someone else can
decrypt it with your equation.
• Try encrypting a new message where you
rotate the number wheel after each letter
youuse. How would you write this cipher so
that someone can decrypt your message?
Think and talk about…
You will need...
sciencemuseumgroup.org.uk/resources
Replace the smaller letter circle with
thenumber circle. Now you can encrypt
messages with numbers instead of letters.
Encrypt messages to a friend in letters
ornumbers, and ask them to send you
encrypted messages too.
Maths in your world
Take the small circle with the letters on it
and put it on the large circle. Secure with
asplit pin in the centre.
Cut out the templates.
Turn the smaller wheel so that each letter
onit lines up with a different letter on the
larger wheel.
Now encrypt your message (make it secret).
For each letter, write down the letter on the
smaller wheel that appears directly beneath it.
Follow these steps…
Encryption is used to send emails and information across
theinternet. Instead of a cipher wheel, a computer uses
reallycomplicated mathematics to encrypt the information.
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