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Bazeries, the man who eventually deciphered the Great Cipher 200 years later, spent months testing if it was a homophone and then spent months testing whether the numbers represented pairs of words. However, due to the fact that everything had to be written out, testing a possibility was extremely tedious, time consuming, and daunting. So, many possibilities needed to be tested out. However, with 576 numbers, each number could mean anything. If it were 26 numbers, it would be somewhat obvious that each number matches a letter. The second reason the Great Cipher took so long to decipher was the technologies available at the time. This great of a mismatch between the quantity of symbols and the quantity of letters had never been seen before, so there was initially a huge gap between the experience of the cryptallaists and the complexity of this cipher. More importantly, however, the Great Cipher included 576 numbers: many more letters than there are in the alphabet. The use of numbers to map to letters had been a relatively new development in cryptography, and cryptanalysts still didn’t know the best method to decipher numeric codes. Still, it was extremely different from all other monoalphabetic ciphers. The Great Cipher was a monoalphabetic cipher, meaning each symbol in the “cipher alphabet” mapped to one and only one thing in the plaintext alphabet. The first reason why the Great cipher took so long to decipher was its complexity compared to ciphers cryptanalysis had seen in the past. It is important to wonder why this particular cipher, which is just an enhanced monoalphabetic cipher, took 200 years to decipher.
![monoalphabetic key cracker monoalphabetic key cracker](https://www.pcrisk.es/images/stories/screenshots201602/truecrypter-decrypterbtc.jpg)
That’s when the Rossingols, cryptanalysts employed by the French government, developed the Great Cipher of Louis XIV.
![monoalphabetic key cracker monoalphabetic key cracker](https://i.imgur.com/Bt4V3LP.png)
People needed a method of encryption that was unbreakable and also not so difficult to use. On the other hand, the newly developed polyalphabetic cipher, a cipher that uses multiple cipher alphabets, was effective but too tedious to be embraced by codemakers.
Monoalphabetic key cracker crack#
Monoalphabetic ciphers had run their course, with cryptanalysts having the resources and know-how to crack any monoalphabetic cipher quickly. I thought about it for a while and I cannot come up with a good way to make the function to rate the ciphertext (as is used in most of the algorithms).The 1600’s were a strange time in the history of cryptography. Is there some reliable (I assume not so fast way) to crack the cipher with only the knowledge and use of the letter frequences and some list of the most lets say 10k or more english words? I googled a bit and all the proposed algorithms like this are some genetic ones (i dont want to get into that) or some advanced (I mean not really basic) statistics (like here and you need some other files). So, I am looking for an algorithm (doesnt have to be really fast) that is fairly simple. This isn’t some big project and it should be fairly simple to do. The key is a permutation of the alphabet. I have decided to make a project at uni that requires me to crack a monoalphabetic substitution cipher.