Cryptography is the art and science of secret writing.
The term is derived from the Greek language:
krytos - secret
graphos - writing
Encryption is the actual process of applying cryptography.
Much of cryptography is math oriented and uses patterns and algorythms
to encrypt messages, text, words, signals and other forms of communication.
Cryptography has many uses, especially in the areas of espionage, intelligence
and military operations. Today, many security systems and companies use
cryptography to transfer information over the Internet or radio for
fears of interception. Some of this encryption is highly advanced, however
even simple encryption techniques can help uphold the privacy of any
everyday person.
The term cryptography also meant the breaking of encrypted messages until
the early 1920s, when the concept of Cryptanalysis began being used
and is now practically an art and science all on its own.
The two main areas of cryptography are Cipher and Code.
Cipher Vs. Code
Code is one of the two major methods of cryptography. This method involves the replacement of complete words or phrases by code words or numbers.
Cipher is the other major method of crpytography. This works on the principal of replacing indivdual letters by other numbers or letter.
More on Code: Most people believe that cipher encryption is harder to break than code encryption. This is not fully the truth. In fact, in code encryption one may have R4D7 meaning I and T600 mean Love and 63U0 meaning You. The code encrypted meassage would be "RD47 T600 63U0". Since, these codes are not based on any kind of patterns, it is almost impossible to figure out, unless you have a code book or you have mutually orginated the codes with others. An example of simple code is the one use on CB radios (eg. ten4, ten30, etc.)
More on Cipher: Since Cipher encryption is based on the replacement of single characters, with other characters and are often based on complex mathematical operations, just looking at the code is discouraging enough to shy of individuals from trying to figure out what it means. An example is: Let's say you replace the 26 letters of the alphabet, marking A-Z off from 1-26. Then you add 5 to each (A would be 6 in this case). To encrypt "I Love You" , you get "14 17202710 302026". This is simple cipher encryption and can be easily broken, nevertheless the result is a totally meaningless number (to the normal eye). Cipher encryption can be produced by hand as it was in the example above. However, since the second world war there have been machines and computers programmed to produce messages using complex algorythms and patterns. There is also the use of a Cipher Key, which is basically a password. The computer can only decrypt the message if the password is the same one used when a message was encrypted. This because the patterns the program uses to encrypt are based on the characters of the password itself. The problem is that, one would only need to know the password to decode the message.
Cipher encryption has more real life applications today, then does code encryption. This is because it is easier to reproduce a program that can cipher and decipher, than it is for a person to learn and memorize a full book of codes. However, both are very good tools for security and privacy purposes
Cryptography Books - Recommended
  Applied Cryptography : Protocols, Algorithms, and Source Code in C, Second Edition
A practical guide in which author Bruce Schneier distills theory, protocols and C algorithms for applications. For best understanding, you should have some familiarity with cryptography, cryptographic algorithms and C code.
  Cryptography: Theory and Practice
A general, comprehensive textbook that treats all the essential core areas of cryptography, from authentication codes to pseudo-random number generation.
  Handbook of Applied Cryptography
A valuable reference for the novice as well as for the expert who needs a wider scope of coverage within the area of cryptography, this book provides easy and rapid access of information and includes more than 200 algorithms and protocols; more than 200 tables and figures; more than 1,000 numbered definitions, facts, examples, notes, and remarks; and over 1,250 significant references, including brief comments on each paper.
  The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography
More of a histroy book than a math book. Throughout the text are clear technical and mathematical explanations, and portraits of the remarkable personalities who wrote and broke the world's most difficult codes. Accessible, compelling, and remarkably far-reaching, this book will forever alter your view of history and what drives it. It will also make yo wonder how private that e-mail you just sent really is.
source: Cipher-Encryption.com
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