Antonio Marzi

Antonio Marzi [1924-2007] served as a radio operator in the Regia Marina from 1940 to 1943. Then he chose to work with the SOE [Special Operations Executive], the British secret service set up by Winston Churchill in 1940.
Equipped with a radio transceiver of 500 miles range, a 1943 MK II, he was parachuted near Verona, in a territory under German occupation and from there he moved near ​​Udine where he  collected and transmitted to the British a lot of detailed military-related information. For that he was equipped with a cipher system to hide the meaning of his radio messages to the Germans, if they had intercepted them.
The Marzi cipher is based on an elegant system of composition and hiding of the key of every single message. It starts from a conventional alphabet created in this way: from the ordinary international alphabet are removed, from their position, the letters of the word RENATO that is moved at the end of the alphabet. All other letters have a symbolic equivalent: a word taken from the poetry of Aleardo Aleardi «Corradino di Svevia» according to the scheme:


Marzi encrypted the message number 36 with the key: GENTILVISOCHIOMA,
where GENTIL is the letter L, VISO is the K and CHIOMA is the H. He arbitrarily chose two more letters [R & E] to form the following block: RLKEH, and added the number 44739 [obtained by complement to 10 of his military record in the Royal Navy, the last digit complements to 9. His military record was: 66370]. From R in the alphabet he dropped four positions and got the T, then, in succession L became S, K became V, E became T and then H became U. TSVTU is the first cipher key Marzi inserted as fourth block of ciphertext. Similarly he proceeded to calculate the key to be added at the end of the encrypted: LEKHR became SOVKF.
At this point let's see the technique for encrypting and decrypting.
The clear message is written horizontally, letter by letter, in the rows of a matrix or table, the width of which, expressed as the number of columns is equal to the length of the key. The height of the matrix, expressed in lines, is given by the ratio of the length of the message and the key length. If the result is zero, then the figure is a full box, otherwise the rest of the division tells us how many other cells must be added after the last line. The clear message is written, line by line, to form an intermediate message obtained in the following way: since in GENTILVISOCHIOMA the first letter of the alphabet is A [at the end of the key] and then the first characters of the intermediate message will take in the column below it: in the first position the first character, in the second the second, and so on to the end of the matrix. Then we go to the second letter in alphabetical order: B, which is not present, then we look for the C, which is present in the sixth from the last position and we continue to take the letters for the intermediate message as we did under the A and so up at the end of the matrix. If a letter occurs more than once we take first the leftmost and proceed with the other to the right, one position at a time, getting the intermediate message or first transposed.
When this first transposition is completed we continue with a second implementation that has the same key. We write the intermediate message line by line and then we take the encrypted message column by column in the order of the key.
Once completed the second transposition, we divide the ciphertext in blocks of five digits, then between the third and the fourth block we add the encrypted text with the first key, and finally we add to its end, the second encrypted of the key and the message is ready to be transmitted in Morse code, with the radio.
At its destination, from the message were removed the fourth and last blocks, which are the encrypted keys. The keyword was calculated as we have seen above, except that in this case 44739 was the subtract number, to get the size of the matrix and the order of insertion of the encrypted message. The encrypted was written vertically until the end, column by column in accordance with the key, then it was taken horizontally in row order. This intermediate message was then rewritten back into the matrix, again column by column following the key to obtain the clear message to be read line by line.