Data Encryption

Data Encryption Computer encryption is based on the science of cryptography, which has been used throughout history. The existence of coded messages has been verified as far back as the Roman Empire. But most forms of cryptography these days rely on computers, simply because a human-based code is too easy for a computer to crack.

Cyptography Definition :-

Cryptography is a discipline of mathematics concerned with information security and related issues, particularly encryption, authentication, and access control. Its purpose is to hide the meaning of a message rather than its existence. cryptography :o concerned solely with message confidentiality (encryption)— conversion of messages from a comprehensible form into an incomprehensible one and back again at the other end o thus rendering it unreadable without secret knowledge (namely, the key).

Most computer encryption systems belong in one of two categories: 1.Symmetric-key encryption ( Private-key encryption ) 2.Asymmetric-key encryption ( Public-key encryption )  Symmetric-key encryption

-> Each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent. -> We should know which computers will be talking to each other so that you can install the key on each one. ->

It is essentially the same as a secret code that each of the two computers must know in order to decode the information

-> The code provides the key to decoding the message. contd….

-> can be divided into stream ciphers and block ciphers. -> Stream ciphers encrypt the bits of the message one at a time. -> Block ciphers take a number of bits and encrypt them as a single unit. Limitations :- The requirement of a shared secret key, with one copy at each end.

- Since keys are subject to potential discovery by a cryptographic adversary, they need to be changed often and kept secure during distribution and in service.

- requirement to choose, distribute and store keys without error and without loss is difficult to reliably achieve. Examples of popular & well-respected symmetric algorithms : - Twofish, Serpent, AES (aka Rijndael), Blowfish, CAST5, RC4, TDES, and IDEA

 Asymmetric-key encryption (Private Key Encryption) :•

uses a combination of a private key and a public key.

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private key is known only to your computer, while the public key is given by your computer to any computer that wants to communicate securely with it

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To decode an encrypted message, a computer must use the public key, provided by the originating computer, and its own private key.

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The sending computer encrypts the document with a symmetric key, then encrypts the symmetric key with the public key of the receiving computer. The receiving computer uses its private key to decode the symmetric key. It then uses the symmetric key to decode the document