Alphabet & Word Correlated Ciphers


Sometimes keywords are used to help encipher a message. By writing out a sentence(s) that contains all the letters of the alphabet you can correlate plain alphabet letters to letters within a word found in the keyword phrase to make the ciphering a bit more difficult to decipher.

The keyword phrase "The quick brown fox jumps over the lazy dog." contains all the letters of the alphabet. Even though some letters appear more than once it shall serve as a keyword phrase because it still contains all the letters of the alphabet. To get started, write out your keyword phrase and number each word:


THE	QUICK	BROWN	FOX	JUMPS	OVER	THE	LAZY	DOG

 1	  2	  3	 4	  5	 6	 7	 8	 9

Then write out your message in the plain alphabet:

Johnson is a spy

To encipher the plain message you find the first word that contains the plain alphabet letter. In the example above, "J" is the first letter to find. It first appears in word five, "JUMPS." Write down the number of the word, 5, and then the the position of the letter from within the word. In this case, "J" is the first letter of the word "JUMPS." Thus, the cipher value for "J" is 51. In other words, "J" is the first character in the fifth numbered word of your keyword phrase.

Use the partially completed cipher below to finish the enciphering process:

J	O	H	N	S	O	N	I	S	A	S	P	Y

51	33	12	35	55	33	35	23	55	82	55

As you can see, letters that repeat like "O" are always the same number since you always find the first word it occurs in. Thus, "O" will always have the value of 33 in the example above. If you are a smart decipherer you'll notice common patterns of numbers that repeat and will be able to figure out which numbers are most likely an "E" or other common vowel or consonant.

Can you figure out a different way to use a keyword phrase to encipher a message? Can you make the cipher above even harder? What are the strengths and weaknesses of the cipher above?

Can you use different phrases as keyword phrases? What must every keyword phrase have in order to work for this type of cipher? Encipher a message using the method above. Then, create a variation on the method above and encipher the message again. Compare and contrast patterns of the two enciphered messages.