Codes And Ciphers

#23 Fractionated Morse Code

#Cryptography

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LECTURE #23: FRACTIONATED MORSE CODE
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[INTRODUCTION]
The Fractionated Morse cipher first converts the plaintext to morse code, then enciphers fixed size blocks of morse code back to letters. This procedure means plaintext letters are mixed into the ciphertext letters i.e. one plaintext letter does not map to one ciphertext letter. This makes it more secure than e.g. substitution ciphers, but it can still be broken with some effort.
One of the benefits of the Fractioned Morse cipher is that it can encipher spaces and punctuation just as easily as letters. The ciphertext message will generally be of a similar length to the plaintext message, but often will have a slightly different number of characters.
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[ALGORITHM]
To pass an encrypted message from one person to another, it is first necessary that both parties have the 'key' for the cipher, so that the sender may encrypt it and the receiver may decrypt it. For the Fractionated Morse cipher, the key is a mixed alphabet e.g. "WATSONBCDEFGHIJKLMPQRUVXYZ".
The first step is to encode our string as Morse code with 'x' between characters and 'xx' between words
Morse Code:
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 −−••

1 •−−−−
2 ••−−−
3 •••−−
4 ••••−
5 •••••
6 −••••
7 −−•••
8 −−−••
9 −−−−•
0 −−−−−

Period •−•−•−
Comma −−••−−
Interrogation ••−−••
Colon −−−•••
Semi-colon −•−•−•
Hypen −•••-
Slash −••-−
Quotation marks •−••−•

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[EXAMPLE]
– Encryption and Decryption –

The text we will encrypt is "Ave Fellow. Well Met!", with a key of "WATSONBCDEFGHIJKLMPQRUVXYZ".

Here is an example of converting text to Morse code:
Plaintext: Ave Fellow. Well Met!
Morse: .-x…-x.xx..-.x.x.-..x.-..x---x.--xx.--x.x.-..x.-..xx--x.x-

Now we take blocks of 3 morse code characters and encipher them using the key and the following table (see attached photo for reference).

The first three morse characters in our message are '.-x', this corresponds to the column with 'N' above it in the key table.

The next three morse characters is '…' which becomes 'W'.

Our complete ciphertext becomes: NWKYSRSBEVKJQKQTSDJC

***Note: The spaces in the plaintext are retained, when we decrypt we will recover any spaces or punctuation from the plaintext.
To decrypt a message, just reverse the process.

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[GAME]
Decrypt this. Don’t comment your answer in the comment section.
NJPYNHQTFMTRELSPTNGHRRELSPTNGHR
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— CICADA —
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