Leopold Samuel Marks (24 September 1920 – 15 January 2001) was an English writer, screenwriter, and cryptographer. During the Second World War he headed the codes office supporting resistance agents in occupied Europe for the secret Special Operations Executive organisation. After the war, Marks became a playwright and screenwriter, writing scripts that frequently utilised his war-time cryptographic experiences. He wrote the script for Peeping Tom, the controversial film directed by Michael Powell that had a disastrous effect on Powell's career, but was later described by Martin Scorsese as a masterpiece. In 1998, towards the end of his life, Marks published a personal history of his experiences during the war, Between Silk and Cyanide, which was critical of the leadership of SOE.
Early life Marks was born into a devout Jewish family. He was the son of Benjamin Marks, the joint owner of Marks & Co, an antiquarian bookseller in Charing Cross Road, London. He was introduced at an early age to cryptography when his father showed him Edgar Allan Poe's story, "The Gold-Bug". From this early interest, he demonstrated his skill at codebreaking by deciphering the secret price codes that his father wrote inside the covers of books. The bookshop subsequently became famous as a result of the book 84, Charing Cross Road, which was based on correspondence between American writer Helene Hanff and the shop's chief buyer, Frank Doel.
Work in cryptography Marks was conscripted into the British Army in January 1942 and trained as a cryptographer; apparently he demonstrated the ability to complete one week's work in decipherment exercise in a few hours. Unlike the rest of his intake, who were sent to the main British codebreaking centre at Bletchley Park, Marks was regarded as a misfit and he was assigned to the newly formed Special Operations Executive (SOE) in Baker Street, which was set up to train agents to operate behind enemy lines and to assist local resistance groups in occupied Europe. SOE has been described as "a mixture of brilliant brains and bungling amateurs". Marks wrote that he had an inauspicious arrival at SOE when it took him all day to decipher a code he had been expected to finish in 20 minutes, because, not atypically, SOE had forgotten to supply the cipher key, and he had to break the code which SOE had regarded as secure. Marks briefed many Allied agents sent into occupied Europe, including Noor Inayat Khan, the Grouse/Swallow team of four Norwegian Telemark saboteurs and his own close friend 'Tommy' Yeo-Thomas, nicknamed "the White Rabbit." In an interview which accompanied the DVD of the film Peeping Tom, Marks quoted General Eisenhower as saying that his group's work shortened the war by three months, saving countless lives. Marks was portrayed by Anton Lesser in David Morley's BBC Radio drama A Cold Supper Behind Harrods. The fictional play was inspired by conversations between Marks and David Morley and real events in SOE. It featured David Jason, and Stephanie Cole as Vera Atkins.
Developments of cryptographic practice One of Marks's first challenges was to phase out double transposition ciphers using keys based on poems. These poem ciphers had the limited advantage of being easy to memorise, but significant disadvantages, including limited cryptographic security, substantial minimum message sizes (short ones were easy to crack), and the fact that the method's complexity caused encoding errors. Cryptographic security was enhanced by Marks's innovations, especially "worked-out keys." He was credited with inventing the letter one-time pad, but while he did independently discover the method, he later found it already in use at Bletchley.
Preference for original code poems While attempting to relegate poem codes to emergency use, he enhanced their security by promoting the use of original poems in preference to widely known ones, forcing a cryptanalyst to work it out the hard way for each message instead of guessing an agent's entire set of keys after breaking the key to a single message (or possibly just part of the key.) Marks wrote many poems later used by agents, the most famous being one he gave to the agent Violette Szabo, The Life That I Have, which gained popularity when it was used in the 1958 film about her, Carve Her Name With Pride. According to his book, Marks wrote the poem in Christmas 1943 about a girlfriend, Ruth, who had recently died in an air crash in Canada; supposedly the god-daughter of the head of SOE, Sir Charles Jocelyn Hambro.
The life that I have Is all that I have And the life that I have Is yours.
The love that I have Of the life that I have Is yours and yours and yours.
A sleep I shall have A rest I shall have Yet death will be but a pause.
For the peace of my years In the long green grass Will be yours and yours and yours.
Gestapo activities and "Indecipherables" Gestapo signal tracers endangered clandestine radio operators, and their life expectancy in occupied France averaged about six weeks. Therefore, short and less frequent transmissions from the codemaster were of value. The pressure could cause agents to make mistakes encoding messages, and the practice was for the home station to tell them to recode it (usually a safe activity) and retransmit it (dangerous, and increasingly so the longer it took). In response to this problem, Marks established, staffed and trained a group based at Grendon Underwood, Buckinghamshire to cryptanalyse garbled messages ("indecipherables") so they could be dealt with in England without forcing the agent to risk retransmitting from the field. Other innovations of his simplified encoding in the field, which reduced errors and made shorter messages possible, both of which reduced transmission time.
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