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book reviews when conditions were right, selection plus establishing with whom one is communicat- replied, and all were caught and executed. recombination would restore the original ing and verifying that their messages have Much of Between Silk and Cyanide con- genetic message. But this is to assume that not been altered en route. Indeed, some of cerns the unfortunate consequences of the selection can act simultaneously at many loci, the earliest forms of writing may have origi- ‘poem code’ initially used by the SOE, and which requires that each of the multitude of nated as a side effect of an authentication Marks’ effort to substitute more secure codes, genetic changes should be separately advan- device — the Sumerian bulla, a sealed clay including the provably unbreakable ‘one- tageous. This is precisely the assumption he vessel containing loose tokens representing time pad’. The poem code was insecure has rejected in order to conclude that inter- the kinds and quantities of goods in an because it depended on having the agent vention from outer space is needed. accompanying shipment. memorize a poem. If the Germans could It is sad to see such a creative mind devot- Users of secret codes have often been guess the poem, or force a captured agent to ed to reaching such an absurd conclusion. It lulled into a false sense of security, with reveal it, they could read all the agent’s previ- might have been better for the reputation of a regard to both secrecy and authentication. A ous messages as well as forging new ones to great scientist if this book had been left to the famous example described by Singh is the their liking, which would be accepted by the decent obscurity of a facsimile edition. ■ encrypted correspondence implicating Mary SOE as authentic. To guard against such forg- John Maynard Smith is in the School of Biological Queen of Scots in Anthony Babington’s plot eries, agents were told to apply certain ‘secu- Sciences, University of Sussex, Falmer, Brighton to assassinate Queen Elizabeth I of England. rity checks’ to their legitimate messages, such BN1 9QG, UK. Trusting the code’s security, Mary used words as a deliberate pattern of misspellings. But that left no doubt of her guilt. Elizabeth’s these security checks were often forgotten, cryptanalyst Thomas Phelippes not only and in any case could also be obtained by broke the code of the intercepted correspon- interrogating the captured agent, who would dence, but even tricked the plotters into have to give some answer consistent with pre- Secrets, codes naming the planned assassins by forging, in viously intercepted transmissions. Many Mary’s hand, an encrypted request for this agents chose to carry an SOE-provided and decoders damning information. Babington, believing cyanide tablet to forestall such interrogation. The Code Book the coded message to be from Mary, duly The improved codes that Marks eventual- by Simon Singh ly put into effect resided not in an agent’s Fourth Estate/Doubleday: 1999. 416 pp. memory but on a piece of silk fabric con- £16.99/$24.95 cealed in their clothing or personal effects. Between Silk and Cyanide: A On the silk was printed a list of random keys, Codemaker’s War 1941–1945 each of which was to be used to encrypt only by Leo Marks one message, then cut off and destroyed. The Free Press/HarperCollins: 1999. 622 pp. security check consisted essentially of a secret $27.50 (hbk)/£6.99 (pbk) password, agreed on between the agent and Charles H. Bennett SOE, which the agent would include in each message before encryption. Cryptography, in its narrow meaning the art Because each message was encrypted by a of secret communication, has always been different random key, the previously inter- the stuff of intrigue, of military campaigns cepted transmissions revealed no informa- and assassinations that succeed or fail tion about the password itself, so a captured depending on whether encrypted messages agent would be free to lie about it without survive the scrutiny of eavesdroppers. being caught in any inconsistency. The Simon Singh’s The Code Book, a popular his- remaining unused part of the silk was, of tory in the tradition of David Kahn’s classic, course, also likely to be captured along with The Codebreakers (Simon & Schuster, 1997), the agent, but, lacking its cut-off portions, it covers the subject from Julius Caesar neither compromised the previously trans- through medieval Arab cryptanalysis, Euro- mitted messages nor enabled the agent’s pean military and diplomatic ciphers of the captors to forge legitimate-seeming new past few centuries, the Second World War’s messages without knowing the password. Enigma and Navajo Code-Talkers, to today’s Meanwhile, the weaknesses of poem code struggles over encryption on the Internet. had contributed to a major guessing game, Basic techniques of cryptography and with the British suspecting that many agents cryptanalysis are carefully explained, as are had fallen into enemy hands, but continuing the archaeological cryptanalyses of Egyptian radio correspondence with them anyway to hieroglyphs and Minoan Linear B. The tech- avoid alerting the Germans of their suspi- nical and historical material is enlivened by cions. In one instance the Germans appar- just the right amount of biographical detail, Ancient Egypt’s ently decided they wanted the British to much of it gleaned from Singh’s interviews know that a certain agent had been captured, with living cryptographers. cryptic hieroglyphs and so staged a Morse code radio drama in Leo Marks’ Between Silk and Cyanide is which the agent, whom Marks believes had far narrower in scope, being a memoir of This ‘praenomen’, or throne name, of Ramses II actually been captured much earlier, was the author’s work between 1942 and 1945 is probably describing him as strong, the chosen heard to begin a normal Morse transmis- in Britain’s Special Operations Executive one of the sun god Re. Many more forms of sion, which then became incoherent, finally (SOE), in charge of communications with writing — from cuneiform to Japanese phonetic breaking off abruptly with a sound like that secret agents in occupied Europe. scripts — are featured in The Story of Writing: of a lifeless hand resting on a telegraph key. An older and perhaps even more impor- Alphabets, Hieroglyphs & Pictograms by The two authors’ styles could scarcely be tant branch of cryptography than secret Andrew Robinson (Thames & Hudson, £9.95). more different. Singh approaches each of communication is authentication: the art of his many topics carefully, balancing human © 2000 Macmillan Magazines Ltd NATURE | VOL 403 | 10 FEBRUARY 2000 | www.nature.com 595 book reviews interest with enough technical detail to make the basic cryptographic principles intelligi- ble to a lay reader. My only regret is that he did not give more weight to authentication and other aspects of cryptography besides secrecy, for example the role of digital signa- tures in electronic commerce. By contrast, Marks’ technical explana- tions are not always intelligible, and are sometimes buried in a torrent of colourful ARCHIVE/CORBIS PICTURE HISTORICAL language: “The ladies of the First Aid Nurs- ing Yeomanry, otherwise known as the coders of Grendon, had force-fed their eight indecipherables with a diet of transposition keys and all but one of the invalids had responded to treatment. The malingerer was waiting on my desk with a curt note from the A heroic national achievement, or an object lesson in taste, mostly bad? Grendon supervisor acknowledging defeat.” Nonetheless, Marks’ book makes exciting involvement in the soft-drinks industry. popular, especially working exhibits. Visitors reading, and is full of information and opin- A reassessment is timely. In 1950, Charles could watch the entire process of cotton ions one cannot find elsewhere. Much of the Gibbs-Smith viewed it as a heroic national production from spinning to finished information in Singh’s book can be found achievement; Nikolaus Pevsner saw it as an cloth. Scientific instruments were found in elsewhere, but not in such an accessible and object lesson in taste, mostly bad; Asa Briggs class X, and included electric telegraphs, enjoyable form. ■ argued in 1954 that it was a defining moment microscopes, air pumps and barometers, as Charles H. Bennett is at the IBM T. J. Watson in the formation of middle-class political and well as musical, horological and surgical Research Center, PO Box 218, Yorktown Heights, economic values, although his later work in instruments. New York 10598, USA. 1988 viewed it as a compendium of ‘things’, Both authors tally the number of medals of Victorian material culture. Others see it as awarded, either for workmanship (Prize the birthplace of modern consumer culture. medals) or for novelty of invention or appli- Both authors here take much from previ- cation (Council medals). They conclude, as ous studies, but have their own perspectives. did some scientific contemporaries, that the A compendium of John Davis is particularly concerned with the British had few reasons for complacency. political and economic context in which the Auerbach is better informed about relevant Victorian culture exhibition evolved, and the way that exhibi- work in scientific history, but perhaps he The Great Exhibition tions could help transform people’s ideas accepts Charles Babbage’s ‘decline of science’ by John R. Davis about industrialization and modernity. His view too readily. Sutton: 1999. 238 pp. £20, $36 analysis of the “modernizing agenda” of The arguments both before and after the The Great Exhibition of 1851: A the organizers has a distinctly familiar feel. exhibition about the role of scientific and Nation on Display Jeffrey Auerbach, on the other hand, is more technical education in industrial progress are by Jeffrey A.