What is Cryptography

Cryptography is the technique of transforming (encrypting) the information into the unintelligible and unreadable form by using a key.  The unreadable form is known as cipher text.  The cipher or encrypted message can only be decrypted by the secret key. Cryptography is important while transmitting the information from one point to another so that no unauthorized user can access and read it. Cryptography uses different methods of encrypting the data and to ensure the secrecy and the privacy of the data communications. 
With the rapid growth of the internet and the online shopping the demand of the electronic security has been increased.  Cryptography is used to protect the online communications, email messages, online transactions, computer passwords, ATM cards transactions, computer data and other secret information.  Cryptography can be classified into the following two types.

• Symmetric-Key Systems

It uses the single key that both the sender and receiver have.

• Public-Key Systems

It uses the two keys a public key that can be used by anyone and a private key that is only used by the recipient of the message.
Cryptography includes the mechanisms such as microdots i.e. merging the words with images and some other ways to hide the secret information.  In today’s computer’s world cryptography is associated with scrambling the plain text into the cipher text and this process is known as the encryption and then converting back the encrypted text into the plain text known as decryption. There are four objectives of the cryptography.

• Authentication. The sender and the receiver can confirm each other’s identity and the source and the destination of the data.
• Integrity. The information cannot be altered without using the secret keys.
• Confidentiality. The information cannot be read or intercepted except the intended recipients.
• Non-Repudiation. The sender and the creator of the information cannot deny his intentions of creating or sending the information.

Cryptographic Algorithms
Cryptography uses the wide range of the algorithms and some of most common algorithms are described below.
RSA:  It is a pubic key system.
MD5: It is a 128 bit message digest system.
HASH:  Has algorithm is used to represent the condensed representation of the fixed length messages.
DES: It is a data encryption standard and a private key system.  It operates on the 64-bit block of data by using a 56-bit key.
AES:  It’s an advanced encryption standard.
HMAC:  It is a hashing method that uses a key in combination with an algorithm such as MD5 or SHA-1.