Free Alphabetical by Michael Rosen

Secret Ways of Writing ). He had been studying the works of previous cryptologists: the Florentine painter, composer, poet, philosopher, zoologist and architect Leon Battista Alberti; a German abbot – Johannes Trithemius; and an Italian scientist – Giovanni Porta. According to Simon Singh, accomplished author of The Code Book , the breakthrough in creating these kinds of multiple-letter codes came in around 1460, when Alberti was having a stroll in the gardens of the Vatican with his friend Leonardo Dato. He went on to write a treatise in 1462 on ciphers called De Cifris where he revealed the wonders of the Alberti Cipher Disk. A version of Alberti’s disc was used by the Confederates during the American Civil War.
    If you’re ingenious, you could make a version of this. Make two discs out of cardboard, one bigger than the other. For the sake of precision, mark each one of them with lines radiatingout from the centre, like bicycle-wheel spokes. Make twenty-six segments, so you have spaces for twenty-six letters. Write each of these in turn at the outermost point in each segment and on each disc. Now place the larger disc underneath the smaller disc. You could stick a split pin through the middle to make rotation of this inner disc easier. In one position, all the letters on both discs match exactly, ‘A’ for ‘A’, ‘B’ for ‘B’, and so on. If you rotate the inner disc by one segment, you will make N + 1. If you rotate the inner disc by three segments, you will make Caesar’s ‘code’, N + 3. These formulae are known as ‘keys’.
    Cunning old Alberti, who also wrote a treatise on the cunning old housefly, worked like this: before writing to you I will tell you a letter. You own a cipher disc. Before starting to read the ciphered message you must set your discs to the letter I’ve told you. Alberti set his inner disc with the ‘K’ on the inner disc matched to the outer ‘B’. ‘If you want to read my message,’ said Alberti, ‘you must use the identical formula you have with you, turning the inner movable disc until the letter B corresponds to the index k.’ What Alberti called an ‘index’ we might call the ‘key letter’. The inner disc provides the letters for the cipher message, the outer for the ‘real’ or ‘plain’ message. He also suggested ways in which you could hide key letters in a message. Very cunning, Alberti.
    Of course, with your discs, you can write whatever you want and in any order on the two discs. Provided the people receiving your message have the same letters and signs on their discs, and they know what are the signals to move the inner disc round, you can make your ciphers yet more undecipherable to the uninitiated. However, if you want to behave as we’ve all done in relation to the internet, you will write a series of messages to people which you think are secret and confidential and then hand your discs and keys to the security services of anothercountry. You will then be surprised that they now know what it is you’ve been writing.
    Between 1938 and 1949, there was an Ovaltine-sponsored radio show in the US called Captain Midnight which would end with a secret message. Listeners wrote to Ovaltine for their ‘Code-O-Graph’ which would enable them to figure it out. In the storyline they were used by agents of the Secret Squadron, a paramilitary organization headed by Captain Midnight. On the outer disc of the ‘Code-O-Graph’ were letters, on the inner disc numbers. Captain Midnight gave you his secret message and you used your ‘Code-O-Graph’ to decipher it.
    The first Code-O-Graph, called the ‘Mystery Dial’ unit, was introduced in 1941, as a device to enable Secret Squadron agents in the field to send and receive secure messages. It was in badge form. The front of the badge displayed the number and cipher alphabet