ORACRYN: Motherland's Wisdom

Chapter 15

"CRYPTOLOGY"

Cryptography or cryptology; from kryptós, "hidden, secret"; and graphein, "writing", or , "study", respectively is the practice and study of techniques for in the presence of third parties called . More generally, cryptography is about constructing and analyzing that prevent third parties or the public from reading private messages; various aspects in such as data , , , and are central to modern cryptography. Modern cryptography exists at the intersection of the disciplines of , , and . Applications of cryptography include , , and .

Cryptography prior to the modern age was effectively synonymous with , the conversion of information from a readable state to apparent . The originator of an encrypted message (Alice) shared the decoding technique needed to recover the original information only with intended recipients (Bob), thereby precluding unwanted persons (Eve) from doing the same. The cryptography literature often uses Alice ("A") for the sender, Bob ("B") for the intended recipient, and Eve ("") for the adversary. Since the development of in and the advent of in , the methods used to carry out cryptology have become increasingly complex and its application more widespread.

Modern cryptography is heavily based on mathematical theory and computer science practice; cryptographic algorithms are designed around , making such algorithms hard to break in practice by any adversary. It is theoretically possible to break such a system, but it is infeasible to do so by any known practical means. These schemes are therefore termed computationally secure; theoretical advances, e.g., improvements in algorithms, and faster computing technology require these solutions to be continually adapted. There exist schemes that provably cannot be broken even with unlimited computing power-an example is the -but these schemes are more difficult to implement than the best theoretically breakable but computationally secure mechanisms.

The growth of cryptographic technology has raised a number of legal issues in the information age. Cryptography's potential for use as a tool for and has led many governments to classify it as a weapon and to limit or even prohibit its use and export. In some jurisdictions where the use of cryptography is legal, laws permit investigators to of encryption keys for documents relevant to an investigation. Cryptography also plays a major role in and of digital media.

"CRYPTOANALYSIS"

Cryptanalysis (from the kryptós, "hidden", and analýein, "to loosen" or "to untie") is the study of analyzing in order to study the hidden aspects of the systems. Cryptanalysis is used to breach security systems and gain access to the contents of encrypted messages, even if the is unknown.

In addition to mathematical analysis of cryptographic algorithms, cryptanalysis includes the study of that do not target weaknesses in the cryptographic algorithms themselves, but instead exploit weaknesses in their implementation.

Even though the goal has been the same, the methods and techniques of cryptanalysis have changed drastically through the history of cryptography, adapting to increasing cryptographic complexity, ranging from the pen-and-paper methods of the past, through machines like the British and at in , to the mathematically advanced computerized schemes of the present. Methods for breaking modern often involve solving carefully constructed problems in , the best-known being .

"CYPHER"

In , a cipher (or cypher) is an for performing or -a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, 'cipher' is synonymous with '', as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially .

Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. There are exceptions and some cipher systems may use slightly more, or fewer, characters when output versus the number that were input.

Codes operated by substituting according to a large which linked a random string of characters or numbers to a word or phrase. For example, "UQJHSE" could be the code for "Proceed to the following coordinates." When using a cipher the original information is known as , and the encrypted form as . The ciphertext message contains all the information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to decrypt it.

The operation of a cipher usually depends on a piece of auxiliary information, called a (or, in traditional parlance, a cryptovariable). The encrypting procedure is varied depending on the key, which changes the detailed operation of the algorithm. A key must be selected before using a cipher to encrypt a message. Without knowledge of the key, it should be extremely difficult, if not impossible, to decrypt the resulting ciphertext into readable plaintext.

Most modern ciphers can be categorized in several ways

By whether they work on blocks of symbols usually of a fixed size (), or on a continuous stream of symbols ().By whether the same key is used for both encryption and decryption (), or if a different key is used for each (). If the algorithm is symmetric, the key must be known to the recipient and sender and to no one else. If the algorithm is an asymmetric one, the enciphering key is different from, but closely related to, the deciphering key. If one key cannot be deduced from the other, the asymmetric key algorithm has the public/private key property and one of the keys may be made public without loss of confidentiality.

BUT THE MYTHOLOGIA IS A LOT MORE DIFFERENT.

(Credits for Wikipidea for the information.)