Bletchley Park
Julius Rosenberg


We’d like to thank everyone who’s played along so far and anyone who may stumble across our creation in the future.  Thank you for your time and your effort as it has validated our own.

At this point some will have found the final answer and others will be stumped but hopefully no one has given up completely.  At least not until tomorrow because as of today our humble project “Bletchley Park” is complete.  Nothing more is needed to reach the end.

Everything must have an end despite convolutions and puzzles.

We hope you will enjoy finding ours, even if you don’t like what you find when you get there.

The point was never to provide an ending so much as an entertainment, a diversion.

We hope your time has been well spent.

Good luck and Goodbye

-Bletchley Park


The story of mankind began in a garden and ended in revelations.


Edward M. Scheidt (born 1939) is the retired Chairman of the CIA Cryptographic Center, and the designer of the cryptographic systems on the Kryptos sculpture at the center of CIA Headquarters in Langley, Virginia.

Scheidt was born in 1939 in California. His father worked for the government, and his mother was a switchboard operator at AT&T. He graduated in 1957 from Cor Jesu High School in New Orleans. He also received a B.A. in computer science from the University of Maryland in 1970, and a degree in telecommunications from George Washington University in 1975. He worked for 26 years at the U.S. Central Intelligence Agency, working primarily in operations, and retired in December 1989.

He is best known for his involvement with part IV of Kryptos (K4), one of the world’s most famous unsolved codes. When the CIA commissioned a new Headquarters building in 1988, the commission for some of the associated artwork was awarded to Jim Sanborn, a Washington DC sculptor who had created some other large public art probjects. After Sanborn researched the themes he wanted to portray in his art, he decided he wanted to incorporate some encrypted messages. Up until that point, Sanborn had never used encryption or text in his work, so he was teamed with Scheidt, who was in the process of retiring. CIA Director William H. Webster referred to Scheidt as “The Deep Throat of Codes”.

In a series of discussions, Scheidt taught various encryption methods to Sanborn, and then Sanborn chose the exact messages to be encrypted. Of the messages on the sculpture, three have been solved, but the fourth section, 97 or 98 characters at the very bottom, remains uncracked. Scheidt said that he does know the answer, along with Sanborn and “probably someone at the CIA”.

After retiring from the CIA, Scheidt helped found an encryption company called TecSec Inc., in 1990 in Vienna, Virginia, where he presently works as Chief Scientist. One of their first ventures was to manufacture portable satellite versions of the secure “STU-III” telephones used by the government. Scheidt manufactured the first model in his home basement workshop, and as of 2002, approximately 500 were in use world-wide by the United States Foreign Service.

Scheidt has been a speaker on cryptography at Bouchercon, a mystery convention. He also volunteers as a local scoutmaster.


Giovanni Soro (died 1544) was a Venetian professional code-cracker. He was more than likely the Renaissance’s first outstanding cryptanalyst and the Western world’s first great cryptanalyst. Soro is known as the father of modern cryptography.

Soro was employed in Venice in 1506 by the Council of Ten as cipher breaker-in-chief. They were the first secret service specializing in codebreaking. Soro ran the cryptanalysis operation in secret as the cipher secretary. Soro’s tasks included deciphering secret messages captured from the messenger spies of Venice’s rivals. At the time, Venice was plagued by espionage and subterfuge. The Council of Ten had its own ciphers changed often so as to impede competitors such as Francois Viete, a French mathematician (father of modern algebraic notation).

Successful diplomacy depended on knowing the adjacent principalities’ thoughts and ideas.  Soro was able to decipher the ciphers of most other courts. By 1510, he had forced most of them to develop their ciphers to a much higher degree of sophistication. As a result, the Papal Curia hired him to break codes their own cipher analysts in Rome could not. Pope Clement VII often sent messages to Soro for cryptanalysis to test their impenetrability.

Soro’s work in Venice continued to take priority over his work at the Vatican. He was Venice’s principal cryptanalyst for almost 40 years. His work is among the earliest successful cryptanalysis which has been preserved. Soro’s reputation was great throughout the leaders of other Italian city-states and Europe. He was so successful that he was given two assistants and a secret office in the Doge’s Palace above the Sala di Segret by 1542. He made Venice a Renaissance bastion of diplomatic cryptology.

Soro wrote a treatise in Italian, French, Spanish, and Latin in the early 1500s on cryptography and solving ciphers which has since been lost.


Conel Hugh O’Donel Alexander, CMG, CBE (19 April 1909 – 15 February 1974) was an Irish-born British cryptanalyst, chess player, and chess writer. He worked on the German Enigma machine at Bletchley Park during World War II, and was later the head of the cryptanalysis division at GCHQ for over 20 years. In chess, he was twice British chess champion and earned the title of International Master. He was usually referred to as C. H. O’D. Alexander in print and Hugh in person.

In February 1940 Alexander arrived at Bletchley Park, the British codebreaking centre during World War II. He joined Hut 6, the section tasked with breaking German Army and Air Force Enigma messages. In 1941, he transferred to Hut 8, the corresponding hut working on Naval Enigma. He became deputy head of Hut 8 under Alan Turing. Alexander was more involved with the day-to-day operations of the hut than Turing, and, while Turing was visiting the United States, Alexander formally became the head of Hut 8 around November 1942. Other senior colleagues included Stuart Milner-Barry, Gordon Welchman, and Harry Golombek. In October 1944, Alexander was transferred to work on the Japanese JN-25 code.

In mid-1946, Alexander joined GCHQ (under the control of the Foreign Office), which was the post-war successor organisation to the Government Code and Cypher School (GCCS) at Bletchley Park. By 1949, he had been promoted to the head of “Section H” (cryptanalysis), a post he retained until his retirement in 1971.

MI5’s Peter Wright, in his 1987 best-selling book Spycatcher: The Candid Autobiography of a Senior Intelligence Officer, wrote about Alexander’s assistance to MI5 in the ongoing Venona project, as well as other important mutual cooperation between the two organizations, which broke down previous barriers to progress. “Any help is gratefully received in this department”, Alexander told Wright, and that proved the case from then on. Wright also lauded Alexander’s professionalism, and opined that the exceptional mental demands of his cryptanalytical career and chess hobby likely contributed to Alexander’s early death at age 64, despite his healthy lifestyle.


Abū Yūsuf Yaʻqūb ibn Isḥāq al-Kindī (Arabic: أبو يوسف يعقوب إبن إسحاق الكندي‎) (c. 801–873 CE), also known to the West by the Latinized version of his name Alkindus, was an Arab Iraqi polymath: an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist. Al-Kindi was the first of the Muslim Peripatetic philosophers, and is known for his efforts to introduce Greek and Hellenistic philosophy to the Arab world, and as a pioneer in chemistry, cryptography, medicine, music theory, physics, psychology, and the philosophy of science.

Al-Kindi was a descendant of the Kinda tribe which is a well known Arabic tribe native of Najd (present day Saudi Arabia). He was born and educated in Kufa, before pursuing further studies in Baghdad. Al-Kindi became a prominent figure in the House of Wisdom, and a number of Abbasid Caliphs appointed him to oversee the translation of Greek scientific and philosophical texts into the Arabic language. This contact with “the philosophy of the ancients” (as Greek and Hellenistic philosophy was often referred to by Muslim scholars) had a profound effect on his intellectual development, and led him to write original treatises on subjects ranging from Islamic ethics and metaphysics to Islamic mathematics and pharmacology.

In mathematics, al-Kindi played an important role in introducing Indian numerals to the Islamic and Christian world. He was a pioneer in cryptanalysis and cryptology, and devised new methods of breaking ciphers, including the frequency analysis method. Using his mathematical and medical expertise, he developed a scale to allow doctors to quantify the potency of their medication. He also experimented with music therapy.

The central theme underpinning al-Kindi’s philosophical writings is the compatibility between philosophy and other orthodox Islamic sciences, particularly theology. Many of his works deal with subjects that concerned theology, including the nature of God, the soul, and prophetic knowledge. However, despite the important role he played in making philosophy accessible to Muslim intellectuals, his own philosophical output was largely overshadowed by that of al-Farabi and very few of his texts are available for modern scholars to examine. However, he is still considered one of the greatest philosophers of Arab descent, and for this reason is known simply as “The Arab Philosopher”.

Al-Kindi was a pioneer in cryptography, especially cryptanalysis. He gave the first known recorded explanation of cryptanalysis in A Manuscript on Deciphering Cryptographic Messages. In particular, he is credited with developing the frequency analysis method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break ciphers (i.e. cryptanalysis by frequency analysis). This was detailed in a text recently rediscovered in the Ottoman archives in Istanbul, A Manuscript on Deciphering Cryptographic Messages, which also covers methods of cryptanalysis, encipherments, cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic. Al-Kindi also had knowledge of polyalphabetic ciphers centuries before Leon Battista Alberti. Al-Kindi’s book also introduced the classification of ciphers, developed Arabic phonetics and syntax, and described the use of several statistical techniques for cryptoanalysis. This book apparently antedates other cryptology references by several centuries, and it also predates writings on probability and statistics by Pascal and Fermat by nearly eight centuries.

Al-Kindi authored works on a number of other important mathematical subjects, including arithmetic, geometry, the Indian numbers, the harmony of numbers, lines and multiplication with numbers, relative quantities, measuring proportion and time, and numerical procedures and cancellation. He also wrote four volumes, On the Use of the Indian Numerals (Ketab fi Isti’mal al-‘Adad al-Hindi) which contributed greatly to diffusion of the Indian system of numeration in the Middle East and the West. In geometry, among other works, he wrote on the theory of parallels. Also related to geometry were two works on optics. One of the ways in which he made use of mathematics as a philosopher was to attempt to disprove the eternity of the world by demonstrating that actual infinity is a mathematical and logical absurdity.


Alan Mathison Turing, OBE, FRS (pronounced /ˈtjʊərɪŋ/, TYOOR-ing; 23 June 1912 – 7 June 1954), was an English mathematician, logician, cryptanalyst, and computer scientist. He was influential in the development of computer science and provided an influential formalisation of the concept of the algorithm and computation with the Turing machine. In 1999, Time Magazine named Turing as one of the 100 Most Important People of the 20th Century for his role in the creation of the modern computer, and stated: “The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine.”  In 2002, Turing was ranked twenty-first on the BBC nationwide poll of the 100 Greatest Britons. His Turing test was a significant and characteristically provocative contribution to the debate regarding artificial intelligence.

During the Second World War, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain’s codebreaking centre. For a time he was head of Hut 8, the section responsible for German naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including the method of the bombe, an electromechanical machine that could find settings for the Enigma machine. After the war he worked at the National Physical Laboratory, where he created one of the first designs for a stored-program computer, the ACE.

Towards the end of his life Turing became interested in chemistry. He wrote a paper on the chemical basis of morphogenesis, and he predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, which were first observed in the 1960s.

Turing’s homosexuality, which was illegal and considered to be a mental illness during his lifetime, resulted in a criminal prosecution in 1952. He accepted treatment with female hormones as an alternative to going to prison. He died in 1954, several weeks before his 42nd birthday, from an apparently self-administered cyanide poisoning, although his mother (and some others) considered his death to be accidental. On 10 September 2009, following an Internet campaign, British Prime Minister Gordon Brown made an official public apology on behalf of the British government for the way in which Turing was treated after the war.

During the Second World War, Turing was a main participant in the efforts at Bletchley Park to break German ciphers. Building on cryptanalysis work carried out in Poland by Marian Rejewski, Jerzy Różycki and Henryk Zygalski from Cipher Bureau before the war, he contributed several insights into breaking both the Enigma machine and the Lorenz SZ 40/42 (a Teletype cipher attachment codenamed “Tunny” by the British), and was, for a time, head of Hut 8, the section responsible for reading German naval signals.

Since September 1938, Turing had been working part-time for the Government Code and Cypher School (GCCS), the British code breaking organisation. He worked on the problem of the German Enigma machine, and collaborated with Dilly Knox, a senior GCCS codebreaker. On 4 September 1939, the day after the UK declared war on Germany, Turing reported to Bletchley Park, the wartime station of GCCS.

Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine which could help break Enigma faster than bomba from 1932, the bombe, named after and building upon the original Polish-designed bomba. The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-protected message traffic.

Replica of a bombe machine

Professor Jack Good, cryptanalyst working at the time with Turing at Bletchley Park, later said: “Turing’s most important contribution, I think, was of part of the design of the bombe, the cryptanalytic machine. He had the idea that you could use, in effect, a theorem in logic which sounds to the untrained ear rather absurd; namely that from a contradiction, you can deduce everything.”

The bombe searched for possibly correct settings used for an Enigma message (i.e., rotor order, rotor settings, etc.), and used a suitable “crib”: a fragment of probable plaintext. For each possible setting of the rotors (which had of the order of 1019 states, or 1022 for the U-boat Enigmas which eventually had four rotors, compared with the usual Enigma variant’s three), the bombe performed a chain of logical deductions based on the crib, implemented electrically. The bombe detected when a contradiction had occurred, and ruled out that setting, moving onto the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. Turing’s bombe was first installed on 18 March 1940. Over two hundred bombes were in operation by the end of the war.


In December 1940, Turing solved the naval Enigma indicator system, which was more mathematically complex than the indicator systems used by the other services. Turing also invented a Bayesian statistical technique termed “Banburismus” to assist in breaking naval Enigma. Banburismus could rule out certain orders of the Enigma rotors, reducing time needed to test settings on the bombes. In 1941, Turing proposed marriage to Hut 8 co-worker Joan Clarke, a fellow mathematician, but their engagement was short-lived. After admitting his homosexuality to his fianceé, who was reportedly “unfazed” by the revelation, Turing decided that he could not go through with the marriage.

In July 1942, Turing devised a technique termed Turingismus or Turingery for use against the Lorenz cipher used in the Germans’ new Geheimschreiber machine (“secret writer”) which was one of those codenamed “Fish”. He also introduced the Fish team to Tommy Flowers who, under the guidance of Max Newman, went on to build the Colossus computer, the world’s first programmable digital electronic computer, which replaced simpler prior machines (including the “Heath Robinson”) and whose superior speed allowed the brute-force decryption techniques to be applied usefully to the daily-changing cyphers.  A frequent misconception is that Turing was a key figure in the design of Colossus; this was not the case. While working at Bletchley, Turing, a talented long-distance runner, occasionally ran the 40 miles (64 km) to London when he was needed for high-level meetings.

Turing travelled to the United States in November 1942 and worked with U.S. Navy cryptanalysts on Naval Enigma and bombe construction in Washington, and assisted at Bell Labs with the development of secure speech devices. He returned to Bletchley Park in March 1943. During his absence, Hugh Alexander had officially assumed the position of head of Hut 8, although Alexander had been de facto head for some time—Turing having little interest in the day-to-day running of the section. Turing became a general consultant for cryptanalysis at Bletchley Park.

In the latter part of the war he moved to work at Hanslope Park, where he further developed his knowledge of electronics with the assistance of engineer Donald Bailey. Together they undertook the design and construction of a portable secure voice communications machine codenamed Delilah. It was intended for different applications, lacking capability for use with long-distance radio transmissions, and in any case, Delilah was completed too late to be used during the war. Though Turing demonstrated it to officials by encrypting/decrypting a recording of a Winston Churchill speech, Delilah was not adopted for use.

In 1945, Turing was awarded the OBE for his wartime services, but his work remained secret for many years. A biography published by the Royal Society shortly after his death recorded:

Three remarkable papers written just before the war, on three diverse mathematical subjects, show the quality of the work that might have been produced if he had settled down to work on some big problem at that critical time. For his work at the Foreign Office he was awarded the OBE.


William Frederick Friedman (September 24, 1891 – November 12, 1969) was a US Army cryptographer (or cryptologist depending on preference). He ran the research division of the Army’s Signals Intelligence Service (SIS) in the 1930s, and parts of its follow-on services into the 1950s. In the late 1930s, subordinates of his led by Frank Rowlett broke Japan’s PURPLE cipher, thus disclosing Japanese diplomatic secrets beginning before World War II era.

Friedman was born Wolfe Frederick Friedman in Kishinev, Bessarabia, the son of a postal worker who migrated to Pittsburgh in 1892. Three years later, his first name was changed to William. As a child, he was introduced to cryptography in the short story “The Gold-Bug” by Edgar Allan Poe. He studied at the Michigan Agricultural College (known today as Michigan State University) in East Lansing and received a scholarship to work on genetics at Cornell University. Meanwhile George Fabyan, who ran a private research laboratory to study any personally interesting project, decided to set up his own genetics project and was referred to Friedman. Friedman joined Fabyan’s Riverbank Laboratories outside Chicago in September 1915. As head of the Department of Genetics, one of the projects he ran studied the effects of moonlight on crop growth, and so he experimented with the planting of wheat during various phases of the moon.

Another of Fabyan’s pet projects was research into secret messages which Sir Francis Bacon had allegedly hidden in various texts during the reigns of Elizabeth I and James I. The research was carried out by Elizabeth Wells Gallup. She believed that she had discovered many such messages in the works of William Shakespeare, and convinced herself that Bacon had written many, if not all, of Shakespeare’s works. Friedman had become something of an expert photographer while working on his other projects, and was asked to travel to England on several occasions to help Gallup photograph historical manuscripts during her research. He became fascinated with the work as he courted Elizebeth Smith, Mrs. Gallup’s assistant and an accomplished cryptographer. They married, and he soon became director of Riverbank’s Department of Codes and Ciphers as well as its Department of Genetics. During this time, Friedman wrote a series of 23 papers on cryptography, collectively known as the “Riverbank publications”, included the first description of the index of coincidence, an important mathematical tool in cryptanalysis.

With the entry of the United States into World War I, Fabyan offered the services of his Department of Codes and Ciphers to the government. No Federal department existed for this kind of work (although both the Army and Navy had had embryonic departments at various times), and soon Riverbank became the unofficial cryptographic center for the US Government. During this period, the Friedmans broke a code used by German-funded Hindu radicals in the US who planned to ship arms to India to gain independence from Britain. Analysing the format of the messages, Riverbank realized that the code was based on a dictionary of some sort, a cryptographic technique common at the time. The Friedmans soon managed to decrypt most of the messages, but only long after the case had come to trial did the book itself come to light: a German-English dictionary published in 1880.

The United States government decided to set up its own cryptological service, and sent Army officers to Riverbank to train under Friedman. To support the program, Friedman wrote a series of technical monographs, completing seven by early 1918. He then enlisted in the Army and went to France to serve as the personal cryptographer for General John J. Pershing. He returned to the US in 1920 and published an eighth monograph, “The Index of Coincidence and its Applications in Cryptography”, considered by some to be the most important publication in modern cryptography to that time. His texts for Army cryptographic training were well thought of and remained classified for several decades.

In 1921 he became chief cryptanalyst for the War Department and later led the Signals Intelligence Sevice(SIS) — a position he kept for a quarter century. In 1929, after The American Black Chamber in New York City was disbanded, its files were entrusted to SIS, and the cryptographic and intelligence services was reorganized to suit its new position at the War Department.

Friedman coined several terms, including “cryptanalysis”, and wrote many monographs on cryptography. One of these (written mostly in his spare time) was the first draft of his Elements of cryptanalysiswhich later was expanded to four volumes, and became the U.S. Army’s cryptographic main textbook and reference. Realizing that mathematical and language skills were essential to SIS’ work, Friedman managed to get authority to hire three men with both mathematical training a language knowledge. They were Soloman Kullback, Frank Rowlett and Abraham Sinkov, each of whom went on to distinguished service for decades. In addition he also was finally able to hire a man fluent in Japanese, John Hurt.

During this period Elizebeth Friedman continued her own work in cryptology, and became famous in a number of trials involving rum-runners and the Coast Guard and FBI during Prohibition.

During the 1920s, several new cipher machines were developed generally based on using typewriter mechanics and basic electrical circuitry. An early example was the Hebern Rotor Machine, designed in the US in 1915 by Edward Hebern. This system offered such security and simplicity of use that Hebern heavily promoted it to investors.

Friedman realized that the new rotor machines would be important, and devoted some time to analysing Hebern’s design. Over a period of years, he developed principles of analysis and discovered several problems common to most rotor-machine designs. Examples of some dangerous features included having rotors step one position with each keypress, and putting the fastest rotor (the one that turns with every keypress) at either end of the rotor series. In this case, by collecting enough ciphertext and applying a standard statistical method known as the kappa test, he showed that he could, albeit with great difficulty, crack any cipher generated by such a machine. Friedman also acquired a commericial version of the German Enigma Machine and developed an algorithm for attacking its cipher which was used years later in the attack on the Japanese Purple Code.

Friedman used his understanding of rotor machines to develop several that were immune to his own attacks. The best of the lot, the SIGABA — which was destined to become the US’s highest-security cipher machine in World War II — was co-invented by Frank Rowlett. At least one patent related to it was finally granted after Friedman had died.

In 1939, the Japanese introduced a new cipher machine for their most sensitive diplomatic traffic, replacing an earlier system that SIS referred to as “RED.” The new cipher, which SIS called “PURPLE,” was different and much more difficult. The Navy’s cryptological unit (OP-20-G) and the SIS thought it might be related to earlier Japanese cipher machines, and agreed that SIS would handle the attack on the system. After several months trying to discover underlying patterns in PURPLE ciphertexts, an SIS team led by Friedman and Rowlett, in an extraordinary achievement, figured it out. PURPLE, unlike the German Enigma or the Hebern design, did not use rotors but stepper switches like those in automated telephone exchanges. Leo Rosen of SIS built a machine — as was later discovered, using the identical model of switch that the Japanese designer had chosen.

Thus, by the end of 1940, SIS had constructed an exact analog of the PURPLE machine without ever having seen one. With the duplicate machines and an understanding of PURPLE, SIS could decrypt increasing amounts of Japanese traffic. One such intercept was the message to the Japanese Embassy in Washington, D.C., ordering an end (on December 7, 1941) to negotiations with the US. The message gave a clear indication of impending war, and was to have been delivered to the US State Department only hours prior to the attack on Pearl Harbor. The controversy over whether the US had foreknowledge of the Pearl Harbor attack has roiled well into the 21st century.

In 1941, Friedman was hospitalized with a “nervous breakdown”, widely attributed to the mental strain of his work on PURPLE. While he remained in hospital, a four-man team — Abraham Sinkov and Leo Rosen from SIS, and Lt. Prescott Currier and Lt. Robert Weeks from the U.S. Navy’s OP-20-G — visited the British establishment at the “Government Code and Cypher School” at Bletchley Park. They gave the British a PURPLE machine, in exchange for details on the design of the Enigma machine and on how the British decrypted the Enigma cipher.

However Freidman visited Bletchley Park in April 1943 and played a key role in drawing up the 1943 BRUSA Agreement.

Following World War II, Friedman remained in government signals intelligence. In 1949 he became head of the cryptographic division of the newly-formed Armed Forces Security Agency (AFSA) and in 1952 became chief cryptologist for the National Security Agency (NSA) when it was formed to take over from AFSA. Friedman produced a classic series of textbooks, “Military Cryptanalysis”, which was used to train NSA students. (These were revised and extended, under the title “Military Cryptanalytics”, by Friedman’s assistant and successor Lambros D. Callimahos, and used to train many additional cryptanalysts.) During his early years at NSA, he encouraged it to develop what was probably the first super-computers, although he was never convinced a machine could have the “insight” of a human mind.

Friedman retired in 1956 and, with his wife, turned his attention to the problem that had originally brought them together — examining Bacon’s supposed codes. Together they wrote a book entitled “The Cryptologist looks at Shakespeare” which won a prize from the Folger Library and was published under the title The Shakespearean Ciphers Examined. The book demonstrated flaws in Gallup’s work and in that of others who sought hidden ciphers in Shakespeare’s work.

At NSA’s request Friedman prepared Six Lectures Concerning Cryptography and Cryptanalysis, which he delivered at NSA. But later the Agency, concerned by the ongoing security hysteria, confiscated the originals from Friedman’s home.

His health began to fail in the late 1960s, and he died in 1969.


Major Friedrich Wilhelm Kasiski (29 November 1805–22 May 1881) was a Prussian infantry officer, cryptographer and archeologist. Kasiski was born in Schlochau, West Prussia.

Kasiski enlisted in East Prussia’s 33rd Infantry Regiment on 20 March, 1823 at the age of 17. In May 1824, he was promoted to the rank of Master Sergeant, and eight months later was commissioned as a Second Lieutenant in February 1825. It took fourteen years to earn his next promotion when, in May 1839, he advanced to the rank of First Lieutenant. His next advancement was quicker, promoted to Captain in November 1842. Kasiski finally retired from active service with the rank of Major on 17 February 1852.

Between 1860 and 1868 he was the commander of a National Guard battalion.

In 1863, Kasiski published a 95-page book on cryptography, Die Geheimschriften und die Dechiffrierkunst (German, “Secret writing and the Art of Deciphering”). This was the first published account of a procedure for attacking polyalphabetic substitution ciphers, especially the Vigenère cipher (although it is possible Charles Babbage was already aware of a similar method but had kept it secret). The method relied on the analysis of gaps between repeated fragments in the ciphertext; such analysis can give hints as to the length of the key used. This technique is known as Kasiski examination.

The significance of Kasiski’s cryptanalytic work was not widely realised at the time, and he turned his mind to archaeology instead. The later years of his life were spent at Neustettin (Szczecinek); the 11th edition of Encyclopædia Britannica cited a scholarly article by Kasiski in its entry on the town. Historian David Kahn notes, “Kasiski died on May 22, 1881, almost certainly without realizing that he had wrought a revolution in cryptology” (The Codebreakers)


Marian Adam Rejewski 16 August 1905 – 13 February 1980) was a Polish mathematician and cryptologist who in 1932 solved the plugboard-equipped Enigma machine, the main cipher device used by Germany. The success of Rejewski and his colleagues Jerzy Różycki and Henryk Zygalski jump-started British reading of Enigma in World War II; the intelligence so gained, code-named “Ultra”, contributed, perhaps decisively, to the defeat of Nazi Germany.

While studying mathematics at Poznań University, Rejewski had attended a secret cryptology course conducted by the Polish General Staff’s Cipher Bureau, which he joined full-time in 1932. The Bureau had achieved little success reading Enigma and in late 1932 set Rejewski to work on the problem. After only a few weeks, he deduced the secret internal wiring of the Enigma. Rejewski and his two mathematician colleagues then developed an assortment of techniques for the regular decryption of Enigma messages. Rejewski’s contributions included devising the cryptologic “card catalog,” derived using his “cyclometer,” and the “cryptologic bomb.”

Five weeks before the German invasion of Poland in 1939, Rejewski and his colleagues presented their results on Enigma decryption to French and British intelligence representatives. Shortly after the outbreak of war, the Polish cryptologists were evacuated to France, where they continued their work in collaboration with the British and French. They were again compelled to evacuate after the fall of France in June 1940, but within months returned to work undercover in Vichy France. After the country was fully occupied by Germany in November 1942, Rejewski and fellow mathematician Henryk Zygalski fled, via Spain, Portugal and Gibraltar, to Britain. There they worked at a Polish Army unit, solving low-level German ciphers. In 1946 Rejewski returned to his family in Poland and worked as an accountant, remaining silent about his cryptologic work until 1967.