Firstly firstly let we understand that what is Cryptography:-

Cryptography is the science of protecting information by transforming it into a secure format. The process, called encryption, happy news for centuries to prevent handwritten messages from being read by unintended recipients. Today, cryptography is used to protect digital data.

????We can also say that Cryptography is associated with the process of converting ordinary plaintext into to an intangible text and vice versa. It is a method of storing and transmitting data in particular form so that only those for whom it is intended can read and process it.

An example of basic Cryptography is encrypted message in which letters are replaced with other characters. To decode the encrypted contents, you would need a grid or table that defines how the letters are transposed.

HISTORY OF CRYPTOGRAPHY:-

Before the modern era, Cryptography focused on message confidentiality - conversion of messages from a comprehensible form into an incomprehensible one and back again at the other end, rendering it unreadable by interceptors aur eavesdroppers without secret knowledge.

The word CRYPTOGRAPHY was coined by combining two Greek words, 'Krypto' meaning hidden and 'graphene' meaning writing.

The roots of cryptography are found in Roman and Egypt in civilization.

The first known evidence of a Cryptography can be traced to the use of 'hieroglyph'. Some 4000 years ago, the egyptians used to communicate by messages written in hieroglyph. this code was the secret known only to the scribes who used to transmit to message on behalf of the kings kings.

Fast forwarding to around 100 bc, Julius Caesar was known to use a form of encryption to convey secret messages to his army generals posted in the war front. This substitution cipher, known as Caesar cipher, is perhaps the most mentioned historic cipher in academic literature.

The earlier Roman method of cryptography, popularly known as the Caesar shift cipher, relies on shifting the letters of message by an agreed number, the recipient of this message would then shift the letters back by the same number and obtain the original message.

Now let we discuss about stenography, stenography is a similar but adds another dimensions to Cryptography. In this method, people not only want to protect the security of an information by concealing it. but they also want to make sure any unauthorised person gets no evidence that the information even exists.

EVOLUTION:-

The the second World war, most of the work on cryptography was for military purposes, usually used to hide secret military information. However, Cryptography attracted attracted commercial attention post-war, with business trying to secure their data from competitors.

the evolution is during and after the European Renaissance, various Italian and papal states led the rapid proliferation of cryptographic techniques. Various analysis and attack techniques were researched in this era to break the secret codes

Improved coding techniques such as Vigenere coding came into existence in the 15th century, which offer the moving letters in the message with a number of variable places instead of moving them the same number of places.

In the early 20th century, the invention of mechanical and electromechanical machines, such as such as the Enigma rotor machine, provided more advanced and efficient means of a codng the information.

Earlier CRYPTOGRAPHY was effectively synonyms with encryption but nowadays Cryptography is mainly based on mathematical theory and computer science practice.

Modern CRYPTOGRAPHY concerns with:

> Confidentiality - Information cannot be understood by anyone.

> Integrity - information cannot be altered.

> Non - repudiation - sender cannot deny his/her intentions in the transmission of the information at the later stage.

> Authentication - sender and receiver can confirm each.