Cryptography is such a broad part of our lives we do not even notice the smallest applications, shopping on eBay or watching satellite television. I bet you even used cryptology when you were in school and did not even know it. Ever write a message in numbers instead of letters? Each letter of the alphabet correlated to its number position in the alphabet. The number sequence 3,16,25,12,20,15,12,15,7,25 equals cryptology. This is a form of cryptology in its most basic form. Webster's dictionary defines Cryptography as : n.
The act or art of writing in code or secret characters; also, secret characters, codes or ciphers, or messages written in a secret code.
The science which studies methods for encoding messages so that they can be read only by a person who knows the secret information required for decoding, called the key; it includes cryptanalysis, the science of decoding encrypted messages without possessing the proper key, and has several other branches; see for example steganography.  Cryptographies main purpose is to hide messages and information. One of the earliest forms of cryptography was the rearranging of letters in messages. This was known as transportation ciphers. A cipher is a system in which plain text, usually the letters, are transposed or substituted according to a predetermined code. Another early form of cryptography was the substitution of letters. One cipher was named after Julius Caesar who was said to have used a 3 letter shift. This involved substituting a letter with another letter in the alphabet three positions away. Caesar used this method to communicate with his generals in wartimes.  Cryptography tries to protect the confidential nature in the communications of military leaders and diplomats. Cryptography was used by early Christians to hide some parts of their writings. One example, 666, the Number of the Beast from the New Testament Book of Revelation, was thought to refer to the Roman Emperor Nero. One of Nero's policies was the persecution of Christians. Lovers are instructed to use cryptography to communicate without being discovered in the Kama Sutra.  Information in original form is called plaintext, the encrypted form is called ciphertext. Texts encrypted by classical ciphers reveal numeric information about the message, which can be used to break the cipher. A classical cipher is a cipher that uses an alphabet of letters and usually is implemented by hand or simple machine. Classical ciphers are no longer used due their simple nature. With the discovery of frequency analysis (around the 10th century), by the Arabs, just about all ciphers of this kind became vulnerable by a fellow cryptographer. Frequency Analysis is based on the commonality of letters in a given language such as st' and th' in the English language. An example would be the letter e is used quite often versus the letter x is rarely used. A basic understanding of the statistics of the plaintext language and some problem solving skills including patience when done by hand are all that is required. These types of ciphers are still used today mostly in puzzles. Practically all ciphers remained vulnerable to this type of attack until Leon Battista Alberti invented the polyalphabetic cipher around the year 1467. His innovation used different ciphers for varying parts of a message. He invented the first automatic cipher device, a wheel which switch alphabets after several words. The polyalphabetic Vigenère cipher uses a key word in controlling letter substitution based on which letter of the key word is used.  Though an improvement, ciphers were still partially vulnerable to frequency analysis techniques. This was discovered in the mid 1800s by Charles Babbage. Modern uses of cryptology date back to World War I. The US was helping the British capture and decipher messages from Germany. At this point in the war the US had remained neutral. Then a telegram was intercepted (The Zimmermann...
References: 3. Eerdmans Commentary on the Bible, James D G Dunn, John W Rogerson, eds., Wm. B. Eerdmans Publishing, 2003, ISBN 0-8028-3711-5
4. Kama Sutra, Sir Richard F
5. David Kahn, The Codebreakers, 1967, ISBN 0-684-83130-9.
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