Cryptography is the technique to make original data changed in some form which makes it difficult to understand and interpret. There are several cryptographic algorithms available present day as described below:

• Secret Key

• Public Key

• Message Digest

Secret Key Encryption

Both sender and receiver have one secret key. This secret key is used to encrypt data from the sender.

Then this key is sent to receiver and then data is decrypted.

The Example of secret key encryption is Data Encryption Standard (DES). In Secret Key encryption, For each host on the network making it difficult to manage, separate key is required.

Public Key Encryption

In this the public key is used to encrypt data at the sender end. At the receiver end the same key is used to decrypt the data.

Example of public key encryption is Rivest-Shamir-Adleman (RSA).

Message Digest

In this method, actual data is not sent, instead a hash value is calculated and sent. The other end user, computes its own hash value and compares with the one just received.If both hash values are matched, then it is accepted otherwise rejected.