Cryptography

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. 1. The act or art of writing in code or secret characters; also, secret characters, codes or ciphers, or messages written in a secret code.

2. 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. [1]

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. [2]

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.[3] Lovers are instructed to use cryptography to communicate without being discovered in the Kama Sutra. [4]

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 Vigenиre cipher uses a key word in controlling letter substitution based on which letter of the key word is used. [2] Though an improvement, ciphers were still partially vulnerable to frequency analysis techniques. This was discovered in the mid 1800s by Charles Babbage.[5]

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 telegram) from Germany to Mexico. Basically what it said was that Germany would divide up the US with Mexico if they would help in the war effort. The US ended its position of neutrality soon after. [6]

In World War II, there were many uses of cryptology. The infamous Enigma machine used by the German military was one of the more famous ones. This was an electro-mechanical, portable cipher machine. It was able to encrypt and decrypt messages. The Enigma machine was a combination of keys, plugs and rotors creating a complex mechanical machine. The Enigma was first commercial available in the 1920's. Governments and military of many nations adopted this type of cryptography. A British mathematician, Alan Turing, was able to crack the code which helped in the Allied victory. The US was also successful in breaking many of the Japanese codes too. This lead to a win at Midway Island, turning the war in the Pacific. Another message that was intercepted lead to the death of Admiral Yamamoto. He was scheduled to visit a naval base in the Solomon Islands, as his plane approached it was ambushed and shot down. The US was not the only country able to break codes. The Japanese were also able to break US codes, with the exception of one. The Navajo language was used as a code. The language was perfect for code because it was an unwritten language and had no alphabet. The idea came from the use of Native American languages in World War I. The Japanese were never able to crack Navajo language code. [6]

Open academic research on cryptography has only been around since the mid-1970s with the Standard, a public specification by the NBS, the Diffie-Hellman paper. [7] Since then, cryptology has become the cornerstone to many aspects of computer and network security with access control and information confidentiality being the most important uses.

Modern cryptology takes on many forms. Digital signatures, electronic commerce, smart cards, digital rights management, computer passwords are among the many applications that use cryptology.

Digital signatures have be come an important part of the business world today. The IRS allows you to digitally sign your online tax return now instead of printing out the forms and mailing them back. Digital signatures eliminate the need to have paper copies signed and mailed back to companies, thus reducing cost of processing and purchasing of the paper. Getting money from your banks ATM requires you to digitally sign in with your pin code. (Personal Identification Number) Online colleges use digital signatures for accepting loans and admission. Many times a combination of your birthday, social security number and some other piece of information is used for verification.

Electronic commerce or ecommerce has been one of biggest growth areas in the past ten years. It is paramount