13 June 2008

The biggest secret?

The first programmable computer was invented by Charles Babbage and Augusta Ada King, Countess of Lovelace.

Charles Babbage’s story is so well known that I don’t need to relate it to you. I also believe that it isn’t completely true. It conceals a secret. We now, of course, are almost certain what part of that secret was.

The first part of the secret was that Charles Babbage broke the The Vigenère cipher some time before 1854. This cipher was the ‘unbreakable’ secret code that had been in use since the mid sixteenth century to transmit military and diplomatic messages. Even the mathematician Charles Lutwidge Dodgson (Lewis Carroll), in 1868, and the Scientific American, in 1917, described the Vigenère cipher as “unbreakable” or “impossible of translation”. The Vigenère polyalphabetic cipher was one of the main codes used by the Russians, and most other western nations, in relaying their military and diplomatic messages.

The value of breaking any code was to keep the fact quiet, so that unsuspecting users would continue to unwittingly reveal their military and diplomatic communications. Once it became known that the code was broken, nobody would use it. As it happened, the major powers continued to use The Vigenère cipher for ten years before a technique for cracking it was published in 1863 by Fridrich Wilhelm Kasiski. Even after that, variants were used until the end of the century. They could be read by the British and American government.

We would probably not even know now that the code had been cracked, were it not for Babbage’s fiery personality. John Hall Brock Thwaites, a Bristol dentist and amateur cryptographer, submitted a “new” cipher to the Journal of the Society of the Arts in 1853; Babbage was stung into pointing out that Thwaites’ cipher was merely a variation of the Vigenère cipher, Thwaites then challenged Babbage to break his cipher. To his surprise, Babbage decrypted a sample, the poem “The Vision of Sin”, by Alfred Tennyson, encrypted according to the keyword “Emily”, the Christian name of Tennyson’s wife. Babbage had evidently done it by analysing the cipher text for patterns of a higher order than simple letter frequencies (Doron Swade 2000)

Whenever an important military encryption system, such as the Enigma Code, is cracked, elaborate ways are devised to keep the fact secret. Selective use must me made of the military or diplomatic intelligence gained as not to alert a hostile agency of the fact that their military secrets were known to their enemy. All trace of Colossus, the first electronic computer, was removed, The existence of Room 40 at the Admiralty, which decoded the “Zimmermann intercept” in January 1917, was kept secret for many years.

Babbage, who was an outstanding mathematician, was fascinated by decryption techniques. At some point he must have realised that to decrypt a mass of routine dispatches, each with their own decryption key, the effort was huge, and the time taken intolerable. One could crack a single message, but to scan the mass of routine dispatches of other nations was impossible to do by hand. What was needed was a machine. The weakness of The Vigenère cipher was already widely suspected, but disregard because of the enormous time and difficulty in cracking a single message. What was needed was a machine that could do it repeatedly and rapidly. It was this idea that, one suspects, drove all Babbage’s energies.

Are there any signs that the British government actually made use of Babbage’s technology to decrypt messages? It is difficult to re-read the brilliant series of moves by Britain against the other European nations between 1850 and 1900 in Africa in consolidating the British Empire without wondering if it was more than just diplomatic skill. It is interesting to re-read the history of the Crimean War with the hindsight that the Russians probably held no secrets from us.

It may not have just been Britain that benefited. We now know that the turning point of the American civil war was Union’s access to the Confederacy’s secret communications, even though they were using the Vigenère polyalphabetic code. In one case they learned, by decoding a message, that the plates for Confederate currency were being manufactured in New York. There are, of course, many stories of the carelessness of the confederacy with their codes, and some of these stories may be true, but one wonders whether they were used to cover up the fact that the Union had got access to a rapid and effective decryption system.

The building of the Difference Engine certainly attracted a great deal of government attention. The work was funded by the British government. The Duke of Wellington, the Chancellor of the Exchequer and other members of the government visited Babbage to inspect the work for themselves. It seems a great deal of attention if the purpose, announced by both Babbage and the government, was merely that of calculating logarithmic, and other mathematical, tables. By February 1830 the government had allocated £9000 towards the project

In 1832 Sir David Brewster, in his ” Natural Magic” wrote “Great as the power of mechanism is known to be, yet we venture to say that many of the most intelligent of our readers will scarcely admit it to be possible that astronomical and navigation tables can he accurately computed by machinery; that the machine may itself correct the errors which it may commit; and that the results of its calculations, when absolutely free from error, can be printed off, without the aid of human hands, or the operation of human intelligence. All this, however, Mr. Babbage’s machine can do, and as I have had the advantage of seeing it actually calculate, and of studying its construction with Mr. Babbage himself, I am able to make the above statement on personal observation”.

In other words, it worked.

Babbage wrote in the “Ninth Bridgewater Treatise, ” Early in the year 1833, a small portion of the machine was put together, and it performed its work with all the precision which had been anticipated.”

In 1834, when the government had put £17000 into the project and Babbage had put £6000 we read that work stopped on the difference engine, against the advice of the entire scientific community.

Was the British government that stupid? What if the project then went underground amidst a smokescreen of pretended obduracy and foolishness? The tools and drawings that had been developed to build the machine mysteriously disappeared, apparently retained Clement, the contractor, in a dispute over payment. Babbage, we are told, lost interest in pursuit of his overambitious Analytical Engine.

Curiously, Babbage, who had just apparently wasted a vast sum of taxpayers’ money,  was offered a Knighthood in 1842. In June, 1843, the portion of the difference engine, as it existed, was placed in the Museum of King’s College, Somerset House. “The portion of the engine was in order, and was capable of calculating to five figures and two orders of differences, at the rate of twelve or fourteen arguments and corresponding tabular numbers per minute; and neither the number of orders of differences, nor the number of digits, would make any difference in its rate of work”.

We know, of course that the government had a working Difference engine. One of Edward Scheutz difference engines, a copy of Babbage’s, and made by Messrs. Donkin for the English Government, later worked in the Registrar-General’s Office in Somerset House. However, it would have been perfectly easy to have manufactured and used several others in complete secrecy without much trouble. After all, the British wartime government managed to construct, use, and dispose of, the first electronic computer, Colossus, without the news ever leaking out.

Could such a thing have been concealed. Well, it was. We didn’t know that Babbage counted code-breaking amongst his hobbies, or that he cracked the ‘uncrackable’ Vigenère cipher until a hundred and fifty years after he did it. What I can’t work out, though is how the Difference engine could be used for assisting in cracking the Vigenère cipher. To solve that puzzle needs a bigger brain than mine.

They call this “bed-work,” “mapp’ry,” “closet-war.”
So that the ram that batters down the wall,
For the great swinge and rudeness of his poise
They place before his hand that made the engine,
Or those that with the finesse of their souls
By reason guide his execution.

Shakespeare, in Troilus and Cressida,’


  • The Science of Secrecy : The Secret History of Codes and Codebreaking. ” Singh, S. Fourth Estate ; ., 2000.
  • The Cogwheel Brain Doron Swade Little, Brown, Marlborough, United Kingdom, 2000

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