Cryptography is full of patterns. Patterns are evident in code-making, code-breaking, and even the history of cryptography itself. Code makers must use some sort of pattern when encrypting any message. Maybe the pattern is as simple as one in a rail fence transposition cipher or as complicated as one in the cipher in the Babington plot. Each encryption will always have some key (or pattern) that it must follow, or else the ciphered message will be as useless to the recipient as it would be to an anonymous third party trying to decipher the message.
Code breakers use similar patterns in order to decipher messages. For Caesar shift ciphers or even mono-alphabetic substitution ciphers, the pattern always begins with frequency analysis. From frequency analysis, all code breakers, whether amateurs or professionals, will attempt to form recognizable words or use clues such as double letter sequences in order to crack the code. Once a few common words, such as “and, the, of,” have been deciphered, the rest of the code can be deciphered with relative ease. Once parts of the code have been deciphered, a pattern tends to emerge in the key used to encipher the text. A key word or phrase may be used, or a pattern such as a shift may be used for the key. This simple pattern works with ciphers as complex as the one used in the Babington plot, as evidenced by the work of Philip Marnix.
The most intriguing pattern is the historical battle between cryptographers and crypt-analysts. Transposition ciphers, which came first, are useless because the text is just as hard to encipher by a crypt-analyst as it is for the intended receiver. Shift ciphers and mono-alphabetic substitutions were very secure until the rise of the Arab caliphate. Since they had so much time and knowledge, new advancements were made in frequency analysis in order to break these ciphers. Soon, nulls were added, and words would be spelled incorrectly in order to throw off potential crypt-analysts. This was largely unsuccessful because the most renowned crypt-analysts of the time could still crack the code with enough words and trying hard enough with frequency analysis. This historical pattern raises a few interesting questions. Will this historical battle ever end? If so, who will emerge the winner? And more importantly, how will important historical events shape this continuous conflict between cryptographer and crypt-analyst?