DPEFT, DJQIFST boe
TFDSFU XSJUJOH.
If for each letter, you instead write
the letter before it in the alphabet,
you will discover what we are doing
this morning.
DPEFT, DJQIFST boe TFDSFU
XSJUJOH.
becomes
CODES, CIPHERS and SECRET
WRITING.
WHY?
Codes have been important throughout
history.
Thousands of people were employed during
the second world war at Bletchley Park,
trying to decipher the codes that were sent
by the Germans to each other.
If they could decipher the code, they could
sink their ships.
WHEN?
Codes have been used since humans could
write.
The Romans used to send messages
throughout their empire using codes to
which only they had the key.
HOW?
Only trusted friends who have the code’s
key can crack the code and read the
message.
CODE 1: SHIFT CIPHER
You previously saw the example
of the SHIFT CIPHER, it gives
each letter in the code a different
letter in real life. The rule is the
alphabet is SHIFTED one way or
another but stays in the same
order. My cipher was:
CODE 1: SHIFT CIPHER
A B C D E F G H I J K L M
B C D E F G H I J K L M N
N O P Q R S T U V W X Y Z
O P Q R S T U V W X Y Z A
The TOP line is what the letter actually is, the BOTTOM line is the one you write in the code.
The letters were moved one place
to the left.
Design your own SHIFT CIPHER
You ‘move’ the alphabet along as many
places as you like but it must be in the
same order.
SEND this message, to a friend, using your
shift cipher.
How many fives in ten
SEND your own message.
Can a partner decode it?
CODE 1: SHIFT CIPHER
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
The TOP line is what the letter actually is, the BOTTOM line is the one you write in the code.
BREAKING THE SHIFT CIPHER
Generally not very reliable.
If you can work out one letter (like the e,
which will occur most often over a long
message) then you can work out all the
other letters as well.
CODE 2: KEY WORD CIPHER
Works in a similar way. The letters are
arranged in order, except the letters from
the key word are taken out and put at the
beginning.
NOTE: the key word must NOT have any
repeating letters.
KEY WORD = FOREST
A B C D E F G H I J K L M
F O R E S T A B C D G H I
N O P Q R S T U V W X Y Z
J K L M N P Q U V W X Y Z
The TOP line is what the letter actually is, the BOTTOM line is the one you write in the code.
DESIGN your own KEY WORD
cipher and write a short message
for a trusted partner to decipher.
You ONLY need to tell them the
KEY WORD, they should not need
your CIPHER sheet.
The KEY WORD cipher is harder
to break than the SHIFT cipher.
The next cipher is even harder to
break. This is because the letters
can be in any order.
Code 3:
The Pigpen Cipher
Devised in 1640 (during the
English Civil war)
Looks like pigs in a pen
Here the letters are represented by
a diagramatical code
The dots are important, if you don’t use them then you will mix up K and X etc.
Do not write the letter, just draw the sides and dots that are next to it.
I
A
M
A
C
O
D
E
B
R E
A
K
E R
DESIGN your own Pigpen cipher
and send a message to a friend
asking how long it is until home
time.
Get them to use their own cipher in
reply.
CODE 4: THE CREASE CODE
Fold a blank piece of A4 paper into 6, so the
fold marks are as below.
Long side
Write your code
on the CREASES
B
Write your code
on the CREASES
i
a
Gg
pleas
O r
Fill the rest up to
make other
words, it is better
if they make
sense.
E a
poa
Is
n
a
M
hed
t
elightful
al
BONUS CODE: ALBERTI’S DISC
You need 2 discs where one overlaps the other.
The inside is the letter you write down the outside
is the real letter (the translation)
Mix the letters up, as you like.
Your partner needs to know the starting point. After
each letter is translated, turn the inner disc one
position clockwise.
Then repeat by translating the next letter and so
on.
Very difficult to break.
CODE 5: WORD GRILLES
These look like a series of random words
until a grille is put over the top to make
sense.
WATCH
LAST FINAL HALF
MONKEY GIRAFFE CIPHER
JUMBLE GOAT COAT HAT
PLEASE FOUND GET
REHEARSE
HOME
AWAY LIGHT DARK
HOUR CODE
OBVIOUS
ANSWER TIME
FIND
LAST FINAL HALF
MONKEY GIRAFFE CIPHER
JUMBLE GOAT COAT HAT
PLEASE FOUND GET
REHEARSE
HOME
AWAY LIGHT DARK
HOUR CODE
OBVIOUS
ANSWER TIME
FIND