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Encryption is a technique to hide data from unauthorized persons by encoding data not to be viewed and modified. Data encryption involves converting the data into encrypted data called cipher text using a mathematical formula called an algorithm.

These algorithms generate a key and then encapsulate the message with this key. There are two types of encryptions as asymmetric and symmetric, are in vogue.

The presentation layer deals with the translation, encryption/decryption, authentication and compression, which are explained below−

It changes the complex data structures used by an application string, integers, structures, etc., into a byte stream that may be transmitted across the network. The message is represented so that communicating machines agree to the format of the data being exchanged. For example, ASCII or EBCDIC character sets.

The translation may be direct or indirect. In the direct translation method, ASCII code is translated as the EBCDIC at the destination machine. In the indirect method, the ASCII code is first translated to a standard format at the source machine before transmission.

It deals with security and privacy issues. Encryption is used to scramble the data so that only authorized persons can unscramble the conversation data. Decryption reverses the encryption process to translate the message back into its original form.

The sender in the source machine uses an encryption algorithm and a key to transform the plaintext (original message) into a cipher text (encrypted message) to encrypt the data. At the destination machine, the reverse process takes place. The receiver has a key and decryption algorithm to translate back the ciphertext into the original plaintext.

There are two types of Encryption which are as follows−

Two mathematically related keys, the name public key and private keys, are generated to encrypt and decrypt the message. Asymmetric encryption is considered more secure than symmetric encryption.

Asymmetric key encryption that involves a key pair as public and private keys involves six major steps−

**Plaintext−**Plaintext is the text message to which an algorithm is applied.**Encryption Algorithm−**It provides mathematical operations to conduct substitutions and transformations to the plaintext.**Public and Private Keys−**They constitute a pair of keys that are used for the encryption and decryption of the message.**Cipher text−**Application of an algorithm on plaintext produces an encrypted or scrambled message.**Decryption Algorithm−**This algorithm is applied to generate the cipher text and the matching key to have the plaintext.

Symmetric encryption, also referred to as conventional or single key Encryption, is based on a secret key, which both communicating parties share. The sending party encrypts the plain text to cipher text message using the secret key. The receiving party on receipt of the cipher text message uses the same secret key to decrypt it to plain text. Examples of symmetric encryption are the RSA algorithm.

Symmetric Notes encryption method has the following five major parts−

**Plaintext−**Plaintext is the text message to which an algorithm is applied.**Encryption Algorithm−**It provides mathematical operations to conduct substitutions and transformations to the plaintext.**Secret Key−**They constitute a part of the algorithm for the encryption and decryption of the message.**Cipher text−**This is the encrypted message generated by applying the algorithm to the plaintext message using the secret key.**Decryption Algorithm−**This encryption algorithm decrypts the cipher text into plain text by using the cipher text and the secret key.

It checks the antecedents of the remote party being the real party rather than an impostor. It defines that the message is received from an authentic person, not from an impostor. A digital signature is one of the several authentication approaches that use the public key encryption method.

It compresses data to decrease the amount of transmitted information, thus saving in bandwidth and money. There are three general methods of data compression. Each method considers that the data stream may be transformed into a more compact representation. This compact data stream is reconstructed back into the original data at the destination machine.

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