Fractionated Morse

History

The Fractionated Morse cipher first appeared in the Apr-May 1960 edition of the American Cryptogram Association (ACA) magazine The Cryptogram and was developed by ACA member FIDDLE. It first converts the plaintext to morse code which is then converted into the cipher using a keyword based lookup table. It is similar to the Pollux and Morbit ciphers but each ciphertext letter represents groups of three morse code characters.

Description

To encipher text using the Fractionated Morse cipher choose a keyword and from it create a keyword mixed alphabet. This is produced by creating a keyed alphabet from the keyword with repeated letters being omitted and followed by the unused letters of the alphabet in alphabetic order. This is then written into a table containing all possible combinations of the three Morse code characters; '.' and '-' to represent the morse code symbols and 'x' to separate the morse groups. These pairs are placed vertically below the keyed alphabet. For example appending unused alphabet letters to the key word CROWDED produces the keyed alphabet CROWDEABFGHIJKLMNPQSTUVXYZ. Writing this into a table gives:

CROWDEABFGHIJKLMNPQSTUVXYZ

.........---------xxxxxxxx

...---xxx...---xxx...---xx

.-x.-x.-x.-x.-x.-x.-x.-x.-

The plaintext is then converted into morse code using the 'x' symbol to separate letters and 'xx' to separate words. If the number of characters is not divisible by three then 'x' is added to the end of the morse code and, if necessary a '.' is added. Finally each group of three morse symbols is replaced with the digit in the same column to create the cipher.

Example

Keyword: CROWDED

Plaintext: Nobody goes there any more because it's too crowded.

N o b o d y g o e s t h e r e a n y

-.x---x-...x---x-..x-.--xx--.x---x.x...xx-x....x.x.-.x.xx.-x-.x-.--xx

I K U O K U B D Z I K T C Z Q O A I F E I H P

m o r e b e c a u s e i t s t o o c

--x---x.-.x.xx-...x.x-.-.x.-x..-x...x.xx..x-x...xx-x---x---xx-.

L K S A Z C T H A M E C T Q X C Z V N L U

r o w d e d

-.x.-.x---x.--x-..x.x-..

I W V M L G T G

Ciphertext: IKUOK UBDZI KTCZQ OAIFE IHPLK SAZCT HAMEC TQXCZ VNLUI WVMLG TG

Solving

Solving methods: Hill Climbing and Dictionary keyword search.