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ENCRYPTION

SYMMETRIC ENCRYTION
Symmetric encryption is the oldest and best technique that contains a secret key(a number, a word, or just a string)of random letters. This key is applied to the text of a message to change the content. Secret key is used to encrypt and decrypt the message by the sender and receiver.
·       Same digital key is used by sender and receiver to encrypt and decrypt message
·       Different set of keys are required for each transaction
·       Length of binary key is used to encrypt data
·       Advanced Encryption Standard (AES) – Most widely used symmetric key encryption. It uses 128,192, and 256-bit encryption keys
·       Other standards use keys with up to 2,048 bits
·       It provides confidentiality of the message.
·       These algorithms tend to be comparatively fast, but they can be used only when involved parties have already exchanged keys.
·       DES, 3DES and AES are examples of symmetric algorithms.
·       The 56-bit keys used in DES are short enough to be easily brute-forced by modern hardware and DES should no longer be used.
·       Triple DES (or 3DES) uses the same algorithm, applied three times with different keys giving it an effective key length of 128 bits.
·        Due to the problems using the DES algorithm, the United States National Institute of Standards and Technology (NIST) hosted a selection process for a new algorithm. The winning algorithm was Rijndael and the associated cryptosystem is now known as the Advanced Encryption Standard or AES.

ASYMMETRIC ENCRYTION
Asymmetric algorithms use two keys, one to encrypt the data, and either key to decrypt. These inter-dependent keys are generated together. One is labeled the Public key and is distributed freely. The other is labeled the Private Key and must be kept hidden.
Often referred to as Public/Private Key Cryptography, these cryptosystems can provide a number of different functions depending on how they are used.
·       The most common usage of asymmetric cryptography is to send messages with a guarantee of confidentiality. If User A wanted to send a message to User B, User A would get access to User B’s publicly-available Public Key. The message is then encrypted with this key and sent to User B. Because of the cryptosystem’s property that messages encoded with the Public Key of User B can only be decrypted with User B’s Private Key, only User B can read the message.
·       Another usage scenario is one where User A wants to send User B a message and wants User B to have a guarantee that the message was sent by User A. User A would encrypt the message with their Private Key. The message can then only be decrypted using User A’s Public Key. This guarantees that User A created the message Because they are then only entity who had access to the Private Key required to create a message that can be decrypted by User A’s Public Key. This is essentially a digital signature guaranteeing that the message was created by User A.
·       A Certificate Authority (CA) may also digitally sign public keys or certificates. We can authenticate remote systems or users via a mutual trust of an issuing CA.
·       PGP and SSL are prime examples of a systems implementing asymmetric cryptography, using RSA or other algorithms.
·       Asymmetric encryption is used to distribute the session key in secret manner.
·       This technique is used to solve the scalability problem related with symmetric encryption.


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