steemit crypto academy||what is cryptography

Salam! Everyone, hope you are doing good.
This is my 1st post in steemit crypto academy
In which I explain about cryptography.

What Is Cryptography?
Cryptography is the process of converting plain text into unintelligible text and vice-versa. It is a method of storing and transmitting data in a particular form.
Cryptography can be used to protect data from theft or user authentication.

CRYPTOGRAPHY CONCEPT:
In cryptography, the concealed information is usually termed "plain text" , and the process of
disguising the plaintext is defined as "encryption", the encrypted plaintext is known as "ciphertext". This process is achieved by number of rules known as "encryption algorithms". Usually, the encryption process relies on "encryption key", which is then given to the encryption algorithm as input along with the information.
Using a "decryption algorithm", the receiving side can retrieve the information using the appropriate "decryption key"[18].

cryptography concept:

CEASER CIPHER:
In cryptography the ceaser cipher technique is one of the earliest and simplest method of encryption technique. It's simply a type of substitution cipher. Each letter of given text is replaced by a letter some fixed number of positions down the alphabet.

ceased cipher encryption wheel:

SIMPLE SUBSTITUTION CIPHERS:
The simple substitution cipher, also known as monoalphabetic cipher. In a simple substitution cipher , we take the alphabet letters and place them in random order under the alphabet written correctly, as seen here:

STREAM CIPHER
Stream ciphers operate an pseudorandom bits generated from the key, and the plain text is encrypted by XORing both the plaintext and the
Pseudorandom bits. Stream ciphers were sometimes avoided in the past.
In a stream cipher, each bit is encrypted individually. There are two types of stream cipher: the first is the synchronous stream cipher and other is asynchronous stream cipher:

synchronous and asynchronous types of stream Cipher:

BLOCK CIPHERS:
This type of cipher of both an algorithm for encryption and an algorithm for dycryption:
•A key (K) is given to the encryption algorithm (E) and a block of plaintext (P), of which C is the product that consists of a ciphertext block. The encryption operation can be expressed as: C=E(K , P).

•As for the decryption algorithm (D), this is the inverse of previous operation in which the cipher text is dycrypted for the plaintext, P. It can b written as: P=D(K , C).

Block Cipher Diagram:

DIGITAL SIGNATURE PRINCIPLES:
Every digital signature aims to fulfill the following 3 requirements: authentication, integrity and non-repudiation . This is known as digital signature application and is the basis of how digital signature work and what they do.

digital signature principle(signing and verifying)

This is my 1st work post submitted to prof. @yohan2on and prof. @kouba01