CHAPTER 1
INTRODUCTION
1.1 CRYPTOGRAPHY
In-order to get security aspects ranging from commerce and payments to the private and public communications there are number of methods proposed till now. Among them cryptography is an important aspect for securing communications in transmitting, receiving and for storage electronic data. But it is necessary to know the method of securing data transmission by Cryptographic technique.
1.2 THE PURPOSE OF CRYPTOGRAPHY
Cryptography is among one of the ancient arts of writing languages in secret code. In 1900 B.C an Egyptian scribe was the first document used inscription for cryptography. Some of the experts argued that cryptography writing has appeared simultaneously after the writing has been invented,
In this method the sender uses a key with some enhanced rules and regulations to encrypt the simple text (plain text) into cipher text that need to send to receiver. The receiver also applies the same enhanced rules to decrypt the cipher text in-order to get the Original content of the message. Actually a single key employs for both process, so it is called as symmetric key cryptography. Figure 1.1 Specific Key Cryptography
Secret key cryptography contains continuous ciphers (stream ciphers) or complex ciphers (block ciphers). Continuous ciphers (stream ciphers) are applied on a single bit (computer word or byte) at a time, so that the key constantly in changing form due to some form of observation (feedback) mechanism employed. The block cipher also employed by same nature but it applies on 1 block of information (data) at the same time by using the similar key on each of the block. In stream cipher plain text will be encrypted to different cipher text but in block cipher plain text block is always encrypted to same cipher data block.
1.3.1.1 Classification of Private Key Cryptography
There are two classes of private-key cryptography scheme which are commonly distinguished as block ciphers and stream
of US in the year of 2001, is a block cipher transforms 128-bit data blocks under a 128-bit, 192-bit or 256-bit secret key, by means of permutation and substitution. In January 1997, the NIST announced the initiation of an effort to develop the AES and made a formal algorithm on September 12, 1997. After reviewed the results of this preliminary research, the algorithms MARS, RC6TM, Rijndael, Serpent and Two fish were selected as finalist. And further reviewed public analysis of the finalist, NIST has decided to propose Rijndael as the new AES on 2nd October 2000. It is expected to replace the DES and Triple DES so as to fulfill the stricter data security requirement because it’s enhanced security