# Cryptography

Posted in Information Technology & Systems, Total Reads: 597

## Definition: Cryptography

The science of encryption and decryption of data is called cryptography. This is generally used for providing security and confidentiality to some message whose secrecy is needed to be mentioned between sender and receiver.

This is generally done by some complex algorithms where a number of operations is performed on the plain text to convert it to cipher text, this method is known as encryption. The reverse of this operation is decryption algorithm, where cipher text is converted back to plain text. Such operations are generally done with the help of keys. In simple terms, a key is used to lock the data and the same key/different key/set of keys is used to unlock the data. The strength of cryptographic algorithm is generally determined by the strength of the algorithm and secrecy of the key.

Example: Suppose Alice wants to send some confidential information about IIT exam paper to Bob. She will convert it to cipher using some key and will sent the cipher text to Bob. Now Bob has got the cipher but to open it he will need the key which will be sent by Alice in a separate mail. To protect data from intruders it is compulsory that cipher text and key should not be sent together.

There are several types of cryptographic algorithms available, some are mentioned below:

a) Conventional cryptography:

I. DES (Data encryption algorithm): This is done by a symmetric key which is of 56-bit. The key can easily be cracked by brute force algorithm.

II. Triple DES: In this the same DES algorithm is applied 3 times in a row which makes the cipher hard to crack using brute force algorithm.

III. AES (Advanced encryption algorithm): In this method 128 bit or 192 bit key is used to encrypt the data. This cipher is also hard to crack using a brute force technique.

b) Public Key Cryptography:

This is an asymmetric cryptography which is done by a set of different keys. In this the plain text is converted to cipher using a public key and is de-ciphered using a private key.

Hence, this concludes the definition of Cryptography along with its overview.

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