|
Cryptology
101 - Part 6
|
►
<-- Back to How a Substitution
Cipher Works
The first thing you need to successfully complete a monoalphabetic
cipher is an agreed upon keyword. It should be something that
the sender and receiver agree upon but not something that anyone
who intercepts you message may guess. The longer your keyword,
or phrase, the more secure the cipher will be.
For our example the key word will be: Godfather
The phrase we will encrypt is:
"I'm gonna make him an offer he can't refuse."
-- The Godfather (1972)
To create the shifted alphabet we begin by writing out the keyword
without repeating any letters. After the keyword we fill in
the rest of the alphabet as it would normally progress. The
table below shows what the shifted alphabet looks like for our
keyword. The keyword is in bold.
|
| Normal Alphabet |
Shifted Alphabet |
| A |
G
|
| B |
O
|
| C |
D
|
| D |
F
|
| E |
A
|
| F |
T
|
| G |
H
|
| H |
E
|
| I |
R
|
| J |
B |
| K |
C |
| L |
I |
| M |
J |
| N |
K |
| O |
L |
| P |
M |
| Q |
N |
| R |
P |
| S |
Q |
| T |
S |
| U |
U |
| V |
V |
| W |
W |
| X |
X |
| Y |
Y |
| Z |
Z |
|
After
we determine the shifted alphabet we use the same method to
write out the ciphertext as we did already with the Caesarian
Shift.
First we write out the plaintext method without and spaces or
punctuation.
imgonnamakehimanofferhecantrefuse
Then using we replace each letter of the plaintext alphabet
for its encrypted partner in the shifted alphabet.
Our final encrypted message is:
rjhlkkgjgcaerjgklttapeadgkspatuqa
And that's how you encrypt a message using a keyword.
Try your hand at Deciphering a Shifted
Message using a Keyword -->
|
