Step 5
Pass the coded message to your friend secretly – perhaps inside a book –
and pass over the RECORDER block at a different time and in a different
place – perhaps leaving it in a special place.
Step 6
Now is the time to see if you can unravel the code yourself, pretending that
you don’t know the answer.
Listen to the key word and, make the code converter again by shifting the
letters 6 places. Unravel the coded message by reading off each letter.
Remember that the code letters are on the bottom and the real letters are on
the top.
❷
THE VIGENÈRE SQUARE
A much cleverer code method is based on the Vigenère square shown
opposite – named after the inventor who was born in 1523. This uses a Key
Word to tell you which row to use to code and decode each letter of your
message. You need to store your Key Word on the RECORDER block and
then pass it to a friend so they can use it to decode the message.
Step 1
Write down your message and then write the key word above it, repeating it
as many times as you need as shown below. To show how this works, we
have chosen the key word “LOGI”. The letters of the key word tell you which
of the rows to use for each letter of your message. We have highlighted the
correct rows to use in the Vigenère Square shown on the next page.
The first letter of the message is ”t” so the L above tells you to use the L row
(No 11). Find the “t” in the top row and move down the column to find the
“E” in the L row. Write this down underneath and move onto the next letter
“o” which is in the O row. Tracing from the “o” in the top row down to the O
row to find the “C”. Repeat this process to encode the rest of the message.
19
L
t
E
Key/Row
Message
Code
O
o
C
G
n
T
I
i
Q
L
g
R
O
h
V
G
t
Z
I
a
I
L
t
E
O
t
H
G
e
K
I
n
V
L
i
T
O
n
B
G
t
Z
I
h
P
L
e
P
O
h
V
G
o
U
I
u
C
L
s
D
O
e
S
