The History and Mathematics of Codes and Code Breaking

Tag: monoalphabetic subsitution

Uncertain Environments Generate Safer Practices

An environment in which one knows he or she must constantly maintain precautions is safer than one where they are unaware of the dangers that potentially exist.  

This concept is exemplified in the case of Mary Queen of Scots by the simple fact that her naive belief that she was speaking in secrecy directly resulted in her death. She essentially signed up for her own funeral by openly disclosing matters of treason. If she had been living in the era in which it was common knowledge that a “codebreaker might intercept and decipher their most precious secrets,” (Singh, p.45) then it is much more likely she would have been less forthcoming with the information she provided in her encrypted messages.

The new environment created was far more advanced than anyone in her time could have predicted. Mary’s generation falls in the era of monoalphabetic substitution, whereas the new age moved on to as many as twenty-six (polyalphabetic). Furthermore, everyone in this new era of cryptography frequently changed their methods. They would not be caught dead using such a basic cipher over a prolonged period of time to transport such crucial information. Even the ciphers used for general business information transported by telegraphs was more secure than the cipher Mary trusted her life with.

The new environment of encryption even allowed for progression in the cryptography field. As ciphers became more complex, more professional codebreakers emerged that continued to prove how difficult it was to create an uncrackable code. In turn, this generated more ciphers and the loop continues from there. Progression did not just make the population more cautious, but it also generated societal growth.

The Greatness of the Great Cipher

I see The Great Cipher is synonymous to the simple monoalphabetic substitution cipher, just on steroids. The concept is the same—one cipher letter or multiple cipher numbers represent a number of plaintext letters. However, what makes the two so different in their difficulty to be cracked lies in the sheer possibility of combinations that could be created from each cipher.

The cipher key was not limited to just one letter replacing another; instead, a few numbers represented syllables. Thus, this opened up a lot more possibilities to stump cryptanalysts.

Before, it was clear in monoalphabetic substitutions that one cipher letter represented one letter of the plaintext. Therefore, we were only faced with a certain amount of different cipher keys to deal with. Even though a completely random monoalphabetic cipher would yield so many possibilities, frequency analysis could easily help decipher it. But now with a cipher with undeterminable characteristics (does “1” represent a letter or does “123” represent one letter? Or a syllable? I’m guessing they did not know how many numbers represented how many letters), patterns that lead to the cracking The Great Cipher become less obvious. There is a multitude of syllables that exist in the French language, making combinations all the greater in amount. This increases the difficulty because although we might see a string of numbers or other patterns, the specific plaintext it refers to—whether it be just one letter or two or three—has much more holes and traps. 

In addition, many people might still be familiar with only the mono alphabetic substitution (since cryptology was still developing), so people might have not thought in a “numbers now represents syllables” way just yet. A reason for the people’s unfamiliarity would be that since the Great Cipher was made by two people (the Rossignols) who already knew how to crack extremely hard ciphers, their knowledge of the weakness of strong ciphers bolstered their knowledge to build something knew that didn’t fall into the traps of the simple mono alphabetic substitution cipher. As such, because they thought five steps ahead of everyone else. In addition to their death, the Great Cipher remained unsolved for 200 years because the only people smart enough to crack hard ciphers and used the weakness of those to create a new super hard to crack cipher had died. In short, their knowledge of the Great Cipher died along with them until it was unearthed 200 years later.

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