Porta Table


Giovanni Baptista della Porta developed the Porta Table cipher method in 1565. The table uses a keyword and the table below to encipher messages. 



	Porta Table     


	A B		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
	C D		a  b  c  d  e  f  g  h  i  j  k  l  m   
			z  n  o  p  q  r  s  t  u  v  w  x  y
	E F		a  b  c  d  e  f  g  h  i  j  k  l  m   
			y  z  n  o  p  q  r  s  t  u  v  w  x   
	G H		a  b  c  d  e  f  g  h  i  j  k  l  m   		
			x  y  z  n  o  p  q  r  s  t  u  v  w    
	I J		a  b  c  d  e  f  g  h  i  j  k  l  m   
			w  x  y  z  n  o  p  q  r  s  t  u  v    
	K L		a  b  c  d  e  f  g  h  i  j  k  l  m   
			v  w  x  y  z  n  o  p  q  r  s  t  u   
	M N		a  b  c  d  e  f  g  h  i  j  k  l  m  
			u  v  w  x  y  z  n  o  p  q  r  s  t    
	O P		a  b  c  d  e  f  g  h  i  j  k  l  m  
			t  u  v  w  x  y  z  n  o  p  q  r  s    
	Q R		a  b  c  d  e  f  g  h  i  j  k  l  m   
			s  t  u  v  w  x  y  z  n  o  p  q  r    
	S T		a  b  c  d  e  f  g  h  i  j  k  l  m   
			r  s  t  u  v  w  x  y  z  n  o  p  q   
	U V		a  b  c  d  e  f  g  h  i  j  k  l  m  
		  	q  r  s  t  u  v  w  x  y  z  n  o  p  
	W X		a  b  c  d  e  f  g  h  i  j  k  l  m  
			p  q  r  s  t  u  v  w  x  y  z  n  o  
	Y Z		a  b  c  d  e  f  g  h  i  j  k  l  m  
			o  p  q  r  s  t  u  v  w  x  y  z  n
To begin, write out your plain message and write out the keyword above it, as shown below:

Keyword:  		JACKET
Plain Message:	LOOK UNDER THE COUCH.


The next step is to use the Porta table to create the enciphered message. Use the letters from the keyword (jacket in the example above) to locate the correct line to use in the Porta table. In the example above "J" is the first keyword letter. Thus, locate "J" on the left hand side of the Porta table - the letters in all uppercase. Once you locate the "J," the 5th set of uppercase letters in the Porta table, you use the letter from the plain message to find the enciphered letter above or below it. In this example the value for "L" in the "J" set is "U". See the example below:

Notice how the letter "O" from the word "LOOK" has a different cipher value because of the different keyword letters. The first "O" is directly under the keyword character "A." Thus, the value of "O" in the "A" set is "B." The second "O" is in the "C" set with a value of "C" for letter "O."

Once the cipher has been written you may want to add in extra characters, like the "z" at the end of my rewritten cipher, to confuse decipherers. Another good idea is to rewrite the cipher, as shown above, into blocks of letters. The example above blocks letters into groups of 3.

To decipher a message encoded with the Porta table you'll need the keyword and the Porta table for reference. Simply write out the enciphered message and the keyword above it. Then, find the corresponding values for each letter, as you did during the enciphering process. When you are all done read the string of letters carefully to separate out the words and rewrite your message as a plain message with spaces and punctuation.