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The Dark History of AlgorithmsZin Derfoufi, a Computer Scienceundergraduate at Queen Mary,delves into some of the darksecrets of algorithms past.Algorithms are used throughout modernlife for the benefit of mankind whetheras instructions in special programs to helpdisabled people, computer instructions inthe cars we drive or the specific steps inany calculation. The technologies thatthey are employed in have helped savelives and also make our world morecomfortable to live it. However, beneathall this lies a deep, dark, secret historyof algorithms plagued with schemes, liesand deceit.Algorithms have played a critical role insome of History's worst and most brutalplots even causing the downfall and riseof nations and monarchs. Ever sincehumans have been sent on secretmissions, plotted to overthrow rulers ortried to keep the secrets of a civilisationunknown, nations and civilisations havebeen using encrypted messages and sohave used algorithms. Such messages aimto carry sensitive information recorded insuch a way that it can only make sense tothe sender and recipient whilst appearingto be gibberish to anyone else. There area whole variety of encryption methods thatcan be used and many people havecreated new ones for their own use: arisky business unless you are very goodat it.One example is the ‘Caesar Cipher’ whichis named after Julius Caesar who used itto send secret messages to his generals.The algorithm was one where each letterwas replaced by the third letter down inthe alphabet so A became D, B becameE, etc. Of course, it means that therecipient must know of the algorithm(sequence to use) to regenerate theoriginal letters of the text otherwise it isuseless. That is why a simple algorithmof “Move on 3 places in the alphabet”was used. It is an algorithm that is easyfor the general to remember. With a plainEnglish text there are around400,000,000,000,000,000,000,000,000different distinct arrangements of lettersthat could have been used! With thatmany possibilities it sounds secure. Asyou can imagine, this would cause anyambitious code-breaker many sleeplessnights and even make them go bonkers!It became so futile to try and break thecode that people began to think suchmessages were divine!But then something significant happened.In the 9th Century a Muslim, ArabicScholar changed the face of cryptographyforever. His name was Abu Yusuf Ya'qubibn Ishaq Al-Kindi – better known to theWest as Alkindous. Born in Kufa (Iraq)he went to study in the famous Dar al-Hikmah (house of wisdom) found inBaghdad. It was the centre for learningin its time which produced the likes of Al-Khwarzimi, the father of algebra - fromwhose name the word algorithmoriginates. It also produced many morescholars who have shaped the fields ofengineering, mathematics, physics,medicine, astronomy, philosophy andevery other major field of learning insome shape or form.Frequency Analysischanged the courseof historyAl-Kindi introduced the technique of codebreaking that was later to be known as'frequency analysis' in his book entitled:‘A Manuscript on DecipheringCryptographic Messages’.His idea was that to decrypt a messageall we have to do is find out how frequenteach letter is in both the sample and inthe encrypted message and match thetwo. If E is most common in English,it is likely to be in the message too.Obviously common sense and a degreeof judgement has to be used whereletters have a similar degree of frequency.Although it is a lengthy process itcertainly was the most efficient of itstime and, most importantly, effective.As decryption became possible, manyplots were foiled changing the course ofhistory. An example of this was how MaryQueen of Scots, a Catholic, plotted alongwith loyal Catholics to overthrow hercousin Queen Elizabeth I, a Protestant,and establish a Catholic England. Thedetails of the plots carried throughencrypted messages were intercepted anddecoded. On 15 October 1586 Mary wason trial for treason. Her life had dependedon whether one of her letters had beendecrypted or not. In the end, she wasfound guilty and publicly beheaded forhigh treason. Walsingham, Elizabeth'sspymaster, knew of Al-Kindi's approach.Today encryption is a major part of ourlives in the form of Internet security andbanking. Learn the art and science ofencryption and decryption and whoknows, maybe some day you mightsucceed in devising a new uncrackablecipher or crack an existing banking one!Either way would be a path to riches! Soif you thought that algorithms were a bore... it just got a whole lot more interesting.8Passionate about computer science?www.cs4fn.org