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By John F. Dooley

The technology of cryptology is made from halves. Cryptography is the research of the way to create safe structures for communications. Cryptanalysis is the examine of ways to damage these structures. The clash among those halves of cryptology is the tale of mystery writing. For over 2,000 years, the will to speak securely and secretly has ended in the construction of various and more and more advanced structures to guard one's messages. but for each process there's a cryptanalyst making a new strategy to holiday that method. With the arrival of pcs the cryptographer turns out to ultimately have the higher hand. New mathematically established cryptographic algorithms that use desktops for encryption and decryption are so safe that brute-force ideas appear to be the one solution to holiday them – thus far. This paintings lines the heritage of the clash among cryptographer and cryptanalyst, explores in a few intensity the algorithms created to guard messages, and indicates the place the sphere goes within the future.

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Continuing in this vein, we would compute the frequencies and draw the charts for the remaining five groups and discover that the keyword for this cryptogram is CRYPTO and the message is It is the strangest cipher I ever encountered, said Mr. Keen. The strangest I ever heard of. I have seen hundreds of ciphers, hundreds secret ciphers of the State Department, secret military ciphers, the elaborate oriental ciphers, symbols used in commercial transactions, ciphers used by criminals and every species of malefactor, and every one of them can be solved with time and patience and a little knowledge of the subject.

So what Friedman had devised was a way to statistically “guess” at the length of the key in a polyalphabetic substitution without having to count the duplicated ciphertext as in the Kasiski method. This is not to say that we can now abandon the Kasiski method. It turns out that hardly ever do you get the expected value when you compute the index of coincidence, so at best, you have to test two key lengths to see if you’ve found the correct one. Also, if the key contains two letters that are the same, like CRYPTOLOGY, then that can throw off the count.

By the 1400s frequency analysis was a well-known technique of cryptanalyzing monoalphabetic substitutions. It was thought that adding a codebook to the cipher system would make the message harder to cryptanalyze, and this does work, up to a point. Several issues arise with the use of nomenclators. First, the size of the codebook is important. The more codewords involved, the more ciphertext must be intercepted in order to make a break in the code. So over time the codebook part of nomenclators grew.

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