cryptography basic

CRYPTOGRAPHY BASICS

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What is cryptography?
cryptography is art of changing any simpler text to a secret code.so how are hacking and cryptography related?hacking is simply gaining access to any system,while the work of cryptography is to encode a simpler text to secret code to provide confidentiality and information security.having knowledge of cryptography helps to make our system more secure.

cryptography is study dealing with mathematics and computers both.so to achieve command on it we have to learn some basic mathematics.
lets catchup some information regarding functions..

what is functions?
let us take Y as a function of X
Domain:the values which is given as input
Range:the values which came as output
So elements in X constitutes domain,and elements in Y which are also called as image constitute range
it is a relation satisfying the below conditions
1.Each element of X should have one image in Y
2.No element in X could have two or more corresponding values in Y
3.Y could have one or more than one values of X
4.It is not mandatory that each element in Y should have corresponding X.

Bijective funtions:functions in which each element in X has only one image in Y and no element in Y should be empty

Inverse function:If Y is made to be codomain then X will automatically become image of Y if the function is bijective function, otherwise inverse of a function is not possible

Trapdoor one way functions:They are the most important type of functions for cryptography.By definition one way function is that function whose inverse is hard to find unless some very essential information is given which is called trapdoor.so for now only we will keep ourselves reserve with this definition only and will exploit trapdoor functions in our next topic