Each letter in the English language has its own unique personality, which includes its frequency and its relation to other letters. It is this personality that allows us to establish the true identity of a letter, even when it has been disguised by monoalphabetic substitution.

The correct use of a strong cipher is a clear boon to sender and receiver, but the misuse of a weak cipher can generate a very false sense of security.

Elsewhere in Europe, other courts were also beginning to employ skilled cryptanalysts, such as Philibert Babou, cryptanalyst to King Francis I of France. Babou gained a reputation for being incredibly persistent, working day and night and persevering for weeks on end in order to crack an intercepted message. Unfortunately for Babou, this gave the k

Stuart Milner-Barry, one of the Hut 6 cryptanalysts, wrote: “I do not imagine that any war since classical times, if ever, has been fought in which one side read consistently the main military and naval intelligence of the other.”

The letters a and l are the most common in Arabic, partly because of the definite article al-, whereas the letter j appears only a tenth as frequently. This apparently innocuous observation would lead to the first great breakthrough in cryptanalysis.

the Abbasid caliphate (or dynasty) heralded the golden age of Islamic civilization. The arts and sciences flourished in equal measure. Islamic craftsmen bequeathed us magnificent paintings, ornate carvings, and the most elaborate textiles in history, while the legacy of Islamic scientists is evident from the number of Arabic words that pepper the l

Secret communication achieved by hiding the existence of a message is known as steganography, derived from the Greek words steganos, meaning “covered,” and graphein, meaning “to write.”

Hence, in parallel with the development of steganography, there was the evolution of cryptography, derived from the Greek word kryptos, meaning “hidden.” The aim of cryptography is not to hide the existence of a message, but rather to hide its meaning, a process known as encryption

Between June 1940 and June 1941 the Allies lost an average of 50 ships each month, and they were in danger of not being able to build new ships quickly enough to replace them.