![]() ![]() On February 8th, 1587, Mary, Queen of Scots was executed after she was tried and found guilty of conspiring to kill her cousin, Queen Elizabeth. Unfortunately, this strategy isn’t as secure as it might sound, and it took a royal beheading to prove that ciphers needed to be refined. For instance, a nomenclature is a cipher alphabet that uses codes. But between the second and fifteenth centuries, only small security improvements were made to ciphers, like the addition of codes – a cryptographic tool that replaces whole words or phrases with other symbols. So, as code breakers became more advanced, cryptographic methods had to improve. So, say you had an encrypted message that began “ piuub gkulvwpev!” By knowing which letters are most common in the language being used, a cryptanalyst can substitute them for the most common letters in the code – and can see that it now reads “ p ERR b gk R l ST p AS!” With these letters filled in, figuring out the rest is easy. And of all those in the field, none were more skilled than the Arab cryptanalysts who, in 750 AD, invented an extremely effective cipher-breaking tool: frequency analysis, which is used to crack a monoalphabetic cipher.Įvery written language uses certain letters and words more often than others, and frequency analysis is designed to identify these characters in a monoalphabetically encrypted message knowing which letters are used the most is a major aid in deciphering a code.įor example, in written English, the most commonly used letters are E, T, A, O, N, S and R. So, ciphers emerged early on, but they were rapidly countered by cryptanalysts, experts who devise strategies to crack codes. This cipher is similar to the Caesar shift except the alphabet starts with a keyword or phrase, at which point the conventional alphabet resumes but without the letters used in the keyword.įor instance, if “Caesar” was the keyword, the alphabet would begin CAESRBDFGHIJK… Therefore A=C, B=A, C=E, D=S, and so on. However, simple Caesar shift ciphers only fooled dedicated adversaries for so long and eventually the keyword cipher alphabet was formed, adding a twist to the monoalphabetic cipher. So, if you shifted the alphabet three places then A=D, B=E, C=F and so on. ![]() It works by using the standard alphabet but shifting the letter it begins on by a set number of characters. įor example, one of the simplest forms of substitution is called the Caesar shift cipher, so named because it was favored by Julius Caesar himself. Since this process forms an alphabet that replaces the conventional one, it is referred to as a monoalphabetic cipher. For instance, A=V, B=X and so on until every letter of the alphabet has a substitute pair, thereby forming a cipher alphabet. ![]() The other method, substitution, is a system wherein one letter stands for another. ![]() For instance, the rail fence cipher, a popular form of transposition, alternates the letters of a message in a zigzag pattern that moves between two consecutive rows. Transposition works by rearranging the letters of a word or sentence to produce a cipher, a secret method of writing. The result was cryptography, a field that simultaneously developed two distinct branches: transposition and substitution. While secret codes might seem like a relatively modern phenomenon, the earliest known form of cryptography, that is, the practice of concealing the meaning of a message, actually dates back to the fifth century BC! It was at this time that Greece, faced with the constant threat of being conquered by Persia, realized that secure communication was essential.
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