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1856 __ The Cryptograph
Charles Wheatstone (1802-1875)
Comment : On March 29, 1856, ‘Chambers’ Journal’ in London reported, “Mr Wheatstone has solved the problem of a method of secret correspondence, easy of application and undiscoverable. He has invented and patented an instrument – the Cryptograph – by means of which any two persons may intercommunicate without fear of betrayal. It is so simple, that the writer, as he sits at the table, turns the barrel with a finger of his left hand, while recording the symbols with his right. These he may send to his correspondent, who, provided with a similar instrument, makes the necessary movements, and reads off the despatch. Or the symbols may be transmitted as a telegraphic message, in full confidence that none but the receiver to whom it is addressed will get at the interpretation. No matter that it be intercepted by anyone having a similar instrument; none but the two who have agreed beforehand the key can find out what is meant. There are two or three forms of the instrument; and one is so contrived as to interpret its own signs at pleasure. We hear that the impossibility of detection by any third or unauthorised person is clearly demonstrable. So unhappy lovers may take heart once more, assured that Mr Wheatstone’s cryptograph will enable them to correspond by cipher-advertisements in the Times to their heart’s content, and without fear of discovery from the most lynx-eyed of guardians. The price of the instrument will be sufficiently moderate – in the advertisers’ phrase – to bring it within the reach of all who may wish to use it.” ‘Scientific American’ gave a more serious and precise description on May 18, 1867: “The importance of a secure cipher for commercial, military and other telegrams of a confidential nature, grows with every step in the extension of telegraphic correspondence, and has brought forth a most ingeniously simple and effective invention for the purpose mentioned, which has been adopted by the British War Office. The parties to a confidential correspondence by telegraph are each furnished with a little instrument consisting of a dial having the letters of the alphabet printed in regular order in a circle near the circumference, with one blank space, making 27 intervals. In a circle within this runs a flanged groove having room for just 26 letters, and in which the letters, printed on separate bit of card of the exact size, are arranged in any arbitrary order understood between the parties. A secure and convenient way to fix this arbitrary order in the mind without risking it on paper, is to agree upon any word easily remembered, and when a despatch is to be sent or deciphered, write down the letters of this word, and under them write the remaining letters of the alphabet in the proper order from right to left, one letter under each letter of the word, then beginning another line under this in the same way, and so on until the entire alphabet in arranged in both lines and columns, which are to be read vertically, and the letters in the inner circle of the dial are to be arranged in that order. After the despatch is sent or deciphered, as the case may be remove the letters, and the instrument is again uncommunicative. But the mode of communication remains to be described. The centre of the dial is penetrated, exactly like a clock, by a shaft or arbour passing through a hollow arbour, the former bearing a long and the latter a short index hand. Each of these arbours has also fixed on its spur wheel, gearing on a loose pinion common to both, so that turning the one turns the other. But the spur wheel of the short hand has twenty-six teeth and that of the long hand twenty-seven, answering respectively to the divisions of the inner and outer circles, so that at every revolution of the long hand, the short hand completes the circuit of the alphabet and one letter further, thus gaining one every time. Consequently, a message spelled out with the long hand, and written out in the letters simultaneously indicated by the short hand, would be in a constantly changing cipher, in which no letter would be represented twice by the same substitute, and no possible clue could be obtained without first obtaining the magic word upon which the inner circle of letters was arranged. The receiver of the message having properly arranged the arbitrary alphabet in the instrument, has only to turn the short hand to the letters of the despatch as received, in succession, and write off those indicated by the long hand. The instrument is, of course, only to be turned forward, or from left to right.” During February 1868 the Company sold four of the cryptograph machines to the Metropolitan Police. These pocket-watch-sized devices could render messages into an unbreakable cipher. Each cost £1 5s. It had been previously adopted by Queen’s household and by that of the Emperor of the French. Thomas Kettle of the Metropolitan Police was later responsible for introducing the cryptograph to the Home Office in London, to the Irish Office in Dublin and to the police at Dublin, Manchester, Liverpool and Birmingham, as well as to the Lancashire Constabulary. These were used to protect government and police messages related to the fight against Fenian terrorism. In October 1867 Superintendant Kettle had been placed in charge of the police telegraphs in London leased of the Company. He spoke approvingly of the simplicity and ease-of-use of both the Universal telegraph and the cryptograph, and of the absolute security of the latter instrument, to Parliament in 1868. The cryptograph was seen at the Exposition Universelle in Paris in 1867, but little further was heard of it in the public press. It was rumoured to be still used, enciphering government secrets, at the end of the century. (Steven Roberts, “Distant Writing - A History of the Telegraph Companies in Britain between 1838 and 1868”, 2010)
Urls : http://distantwriting.co.uk/privatetelegraphy.aspx (last visited )

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