Introduction to Cryptogyaphy

Cryptography is a technique which is used for security purpose. It is mainly used in defense Department although it can be used in general purpose but mainly it used for secure data. There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting passwords. It is one of the important aspect for secure communication between users, this facts is mainly focus in this chapter.

But it is important to note that while cryptography is necessary for secure communications, it is not by itself sufficient. The reader is advised, then, that the topics covered in this chapter only describe the first of many steps necessary for better security in any number of situations.
This paper has two major purposes. The first is to define some of the terms and concepts behind basic cryptographic methods, and to offer a way to compare the myriad cryptographic schemes in use today. The second is to provide some real examples of cryptography in use today.

I would like to say at the outset that this paper is very focused on terms, concepts, and schemes in current use and is not a treatise of the whole field. No mention is made here about pre-computerized crypto schemes, the difference between a substitution and transposition cipher, cryptanalysis, or other history. Interested readers should check out some of the books in the bibliography below for this detailed - and interesting! - background information.

TYPES OF CRYPTOGRAPHIC ALGORITHM

There are several ways of classifying cryptographic algorithms. They are categories on basis of keys that are employed for encryption and decryption, and further defined by their application and use. The three types of algorithms possible in cryptography. that are shown below.

Secret Key Cryptography: Uses a single key for both encryption and decryption

Public Key Cryptography: Uses one key for encryption and another for decryption

Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information Public Key Cryptography

1. Secret Key Cryptography:
   
   In this a single key is for encryption and decryption. In this the sender uses the key to encrypt the plaintext and sends the cipher text to the receiver and The receiver applies the same key to decrypt the message and recover the plaintext because only a single key is used for both encryption and decryption.
 

2. Public Key Cryptography
   
   In this we described a two-key crypto system in which two parties could engage in a secure communication over a non-secure communications channel without having to share a secret key. In Public key Cryptography we use two separate key one for encryption and other for decryption.
    
3. Hash Functions
   
   Hash functions, also called message digests and one-way encryption. Hash functions are also commonly employed by many operating systems to encrypt password.