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Rapid advancements in technology world resulted in the drastic growth in the amount of data transferred through the network. The network used for the multimedia communication does not provide much security for the data transfer as well as the digital communication. During this time, tens of millions people using the internet options for essential communication and is being a tool for commercial field increased, So that security is an enormously important issue to deal with. And the Web services also having data storage and data communication, we need to be protected and providing confidentiality of this web service from piracy and eavesdropping. Hence we necessitate recognizing the different aspects of security and their applications. Many of these applications ranging from secure commerce, protecting passwords or pin and payments to private communications. As we know, one of the essential aspects of secure communication is Cryptography. Simple description of cryptography is the science of writing secret codes. Here we are thrash out and reflect the historic expedition of cryptography.
Before achieve to the historic view of cryptography, let us discuss what cryptology is. A cryptosystem or a cipher system is a technique used to conceal information from unintentional user. Cryptography is the science of creating that kind of cryptosystem where as cryptanalysis is the scientific art of unraveling these cryptosystem when it is read by any pirate. Both cryptography and cryptanalysis encompass by the term cryptology. In this cryptography, encryption and decryption are the two major processes in that. Encryption is the process of renovate plain text into cipher text. Here plain text is the original form of message while cipher text is the unrecognizable form of information. The typical reverse process of encryption is called as decryption. Certain algorithms are used to decrypt and encrypt the information. The selection of these algorithms depends upon the nature of the medium which is used to transmit the information. These algorithms are simply calling it as encryption algorithms and decryption algorithms.
History of cryptography and cryptanalysis:
As we know, cryptography is the major aspect of security. The term cryptography is coming from Greek word 'Îºryptos and graphing ', meaning is hidden or secret. It is the study of security technologies and performs in the presence of third parties. More generally, cryptography is the science of privacy and is an ancient art. It is about constructing and analyzing the protocols that overcomes the authority of adversary and which are correlated with various aspects of information security such as data integrity, non-repudiation and confidentiality and authentication. INTEGRITY: it is the conception of stability methods, values, actions, principles and expectations. We can test the integrity of the system either objectively or subjectively. NON-REPUDIATION: it refers to the status of affairs where the self-styled creator of the statement will not be capable to effectively test the validity of the contract. CONFIDENTIALITY: it is the ethical standard of caution associated with the profession such as law, medicine etc.: it is preferably needed in all the fields it is related to the secrecy of the data and more precise, the secrecy tone of a voice. AUTHENTICATION: it is the act of confirming the reality of an aspect of an entity. This might grip the conforming the uniqueness of a person, software programs etc.:
Before the modern era, message confidentiality is solely depends on the cryptographic methods. The communication of messages from graspable form into an impenetrable one and acknowledgement back again from the other end without interpreting by pirates. To ensuring secrecy in communication encryption is worn up in the fields of conversation between the military leaders, diplomats and those of spies. Encryption and cryptography are nurturing to synonym in this era. Mainly, encryption and decryption used for privacy. Encryption algorithms are supported in achieving this privacy on each transmission over a network.
The earliest cryptography was the form of simple writing messages, as most of the people could not read this. It was solely concerned about the converting messages into the scribbled manner of figures to protect the message during the time of transmission of message from place to place. The need of cryptography arose because of the advance in our life mode. As we know, necessitate to obscure message has been with us moved out of caves, started living in groups and decided to seize this civilization scheme seriously. As soon as there were different groups or tribes, the basic idea was that we had to work against each other along with the terms of secrecy, crowd management and level of aggression. The most basic forms of cryptography were established in the crib of civilization including the region encompassed by Egypt, Greece and Rome. We have the history of cryptography at least 4000 years. The history of cryptography can be discussed in the three titles are; Classical cryptography, medieval cryptography and modern cryptography.
As early as 1900 B.C, Egyptian scribes used hieroglyphs in substandard fashion, most probably to conceal the sense from those who did not know the meaning. As for the Greek's for using a stick, the method was known as letter shifting or substitution. It was very simple matter of trying out sticks of various diameters until the messages became understandable. The writing would be meaningless while the tape was unwound. The Romans also found their own methodology was known as a Ceaser shift cipher. This name originated because of Julius Ceaser. In his correspondence, he allegedly uses the simple substitution method. Then Romans utilized the idea of shifting letter by a granted numbers and writing information in this historical manner simply calls it as letter shift. The receiver side used the same method to decipher.
The timeline of cryptography showed us that, Hebrews also enciphered certain words in the scriptures anciently. In 1200s, Roger Bacon described various methods and the famous Geoffrey Chaucer included different ciphers in his works consequently. Then in 1460's, Leon Alberti devised a cipher wheel and defines the principles of frequency analysis. And then published a book on cryptology by Blasé de Vigenere in 1585. He described about poly alphabetic substitution cipher also.
The classic cryptographic having two components known as classic cipher, named as, substitution ciphers and transposition ciphers. In substitution ciphers, letters are replaced by other letters while in transposition the letters are arranged in a different fashion. According to the combination of these ciphers, it can be classified as two are; mono alphabetic and poly alphabetic. Mono alphabet having only one substitution or transposition used even as poly alphabetic having several substitutions or transposition used. Several such ciphers concatenated mutually to form a product cipher. The Ceaser shift cipher is an example of a mono alphabetic cipher. While comparing with poly alphabetic, mono alphabetic method of encryptions is very easy to break. Here only one time substitution is possible. It is easy to make the sense of the message. Frequency analysis of each letter in the encrypted messages makes easy to decrypt. But in case of poly alphabetic, rearranging the letter in n-grams (anagramming) gives the highest frequency. Hence frequency analysis no more supported.
Generally, assured keys are used to encrypt and decrypt the messages in the communication. In classical cryptography, both sender and receiver share the common key, this key may be the same or trivial to derive from one another. Sometimes it is called as symmetric cryptography. The serious practical drawback of classical cryptography is based on the key distribution problem. Otherwise, potential user has to agree secretly and in advance on the key must be long, random sequence of 0's and 1's. Once we have done this they can use keys for encrypting and decrypting. And the rest of the cryptograms can be transmitted by publicly without compromise the security of information. Most of the time forced to send key along with the messages. Hence we need a secure medium for transmitting. Such a secure medium is usually available only at certain time or under assured circumstances.
The timeline is not at all finished here. Many mechanical encryption or decryption devices are invented in the 20thy century. Jefferson cylinder developed and comprised 36 disks device with a random alphabet in 1970's. Wordsworth in 1817 invented the Wheatstone disc. But it is actually developed by Wheatstone in 1860's. Here comprised two concentric wheels were used to generate a Polyalphabetic cipher. One of the most important encryption machine, named as Enigma rotor machine heavily used in the Second World War. Here series of rotor wheels comprised with internal cross-connections which is providing substitution with incessantly shifting alphabet.
The science and art of cryptography showed no further changes or advancements until the middle ages. At that time, methodology of cryptography was used by all the western European government in one form to another. The major use of cryptography in that era is keeping touch with ambassadors. Especially Leon Battista Alberti was known as "the father of western cryptography" at that time due to his invention in poly alphabetic substitution. He used two copper disks on his method that fit together. The alphabet extolled on each of these disks. After every few alphabets, the two disks were rotated to modify the encrypting sense. Thus the preventive use of frequency analysis to split cipher. Polyalphabetic substitution went throughout a range of changes and is most especially attributed to Vigenere, even if Rubin claims that he in fact had nothing to do with its creation. Rubin further points out that the use of the cipher disks continued during the Civil war. Although the North regularly cracked the messages With the South using brass cipher disks.
In 1918, Gilbert Vernam worked to develop the broken cipher and created a new cipher called as Vernam-Vigenere cipher. But the drawback is they are unable to modify the greater strength on it. His works helps to invent one time pad which is typical keyword use for once and it provide greater security to prevent near unbreakable. Even criminals also used the cryptographic methods during the proscription to communicate with others, was reported by Whitman. In addition to this, it is vital to declare about the newly popularized "Windtalkers". The Navajo's used own languages as a source for cryptography. The code was not at all broken and was involved in the success in the Pacific Theatre during WWII. A dispute could be finished that the spoken language was not strictly cryptography, but it should be noted that in each communication, the message was written behind as a matter of method.
In this modern era, the drastic growth of cryptography and its techniques were originated from basic message confidentiality to include various phases of message integrity checking, digital signers and sender or receiver identity authentication with the other things. The modern field of cryptography can be divided into various areas of study. Let us discuss here the major chiefs:
SECRET KEY CRYPTOGRAPHY:
In secret key cryptography, a single key is used for both encryption and compression. In this technique, the sender uses a single or various sets of instruction to make cipher text from plain text and sends encrypted data to receive. The receiver uses a similar key for the decryption also. Hence it is oblivious that the key must be known to both sender and receiver. But in that, distribution of key is the biggest difficulty faced up. Secret key cryptography schemes are classified into stream cipher or a block cipher. A stream cipher is defined as operating on a single bit at a time and implements some from feedback mechanism. Hence the key is continuously changing. It has several flavors, but most important two is self synchronizing ciphers and synchronous ciphers. In a block cipher, at a time schema encrypts one block using the same key on each block. Block ciphers can have several modes of operation. Most important modes are electronic codebook (ECB), cipher block chaining (CBC), cipher feedback (CFB), output feedback (OFB). Mainly secret key cryptography is used in DES, AES, BLOWFISH, TWOFISH, RIVEST CIPHERS etc.:
The cryptographic hash function is the third type of cryptographic algorithm. Hash functions are an algorithm that uses no key, is also called message digests and one-way encryption. Instead of a key, a fixed length hash value is computed based upon the length of the plain text to be recovered. It is also employed to encrypt passwords by many OS and provide a measure of file integrity. Generally hash algorithms are used to provide a digital fingerprint of a file's contents. Hash algorithms are commonly used in MD algorithms, SHA (secure hash algorithm), RIPEMD, whirlpool etc.:
PUBLIC KEY CRYPTOGRAPHY:
Public key cryptography is the most significant development in cryptography in last 400 years. Mainly this technique depends upon the existence of called as one way functions or mathematical functions. A pair of key is required, one is for encrypting the data and another is used for decrypting the data and this approach is also called asymmetric cryptography. In asymmetric cryptography, one of the keys designed as public key which is advertised as widely as the owner wants. The other key is the private key, is never revealed to another. The need of this cryptography is occurring due to the secretly establishing keys between the communities while does not exit a secure channel for communication. As we discussed above, a pair of keys is used in this algorithm. While Hellman and Diffie might not find such a system, they just present a Diffie-Hellman key exchange protocol for public key cryptography. Now widely this idea used for secure communication to permit users with a secret agreement on shared encryption key. Publication by Diffie and Hellman widely spread and inspired to find out the public key cryptography. Finally Ronald Rivest, Adi Shamir and Len Adleman won the race by discovering an RSA algorithm in 1978. In addition to both of this algorithm are used more widely, Caremer-Shoup Cryptosystem, ElGamel encryption and other various elliptic curve techniques are also included. In 1997, Government Communications headquarters (GCHQ) published a document which reveals that cryptographers at GCHQ had expected various educational developments.
In around 1970, James H. Ellis had conceived the values of public key cryptography. Then in 1973, Clifford Cocks developed a solution that almost similar to the RSA algorithm. And Malcolm J. Williamson is claimed to have developed the Diffie-Hellman algorithm in 1974. Public key cryptography is also used in the scheme of digital signature for implanting. Simply digital signature is a suggestion of a normal message; they have the feature of being very easy for the user to produce but very difficult forge by others. In digital signature there are basically two algorithms, one is for signing and other is mainly for verification. RSA and DSA are the most popular digital signature schemes.