What is cryptography? Algorithms to keep message secret in network

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Cryptography is the study of security over communication between senders and receivers message so that only right recipient can get the message and processed it.The term is derived from the Greek word kryptos, which means hidden.Mechanise of hiding the secret message with encryption is called cryptography. Art of manipulating the original with so algorithms.

Cryptography is not new but its derived from our Ancient history.Famous example from there is lemon secret message send over the paper.

Cryptography is closely related to the disciplines of cryptology and crypt-analysis.

Objectives of cryptography

Confidentially : Unauthorised person cannot get the information.
Integrity : The information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected.
Non-Repudiation : The creator/sender of the information cannot deny at a later stage their intentions in the creation or transmission of the information.
Authentication : The sender and receiver can confirm each other’s identity and the origin/destination of the information.
Access Control: Requires that access to information resources may be controlled by or the target system.
Availability: Requires that computer system assets be available to authorised parties when needed.

Network Security Mechanism

One of the most specific security mechanisms in use is cryptographic techniques. Encryption or encryption-like transformations of information are the most common means of providing security. Some of the mechanisms are

Encipherment

Digital Signature

Access Control

Network security attacks

security attacks

Cryptographic Attacks

Passive Attacks : Passive attacks are in the nature of eavesdropping on, or monitoring of, transmissions. The goal of the opponent is to obtain transmitted information.

Active Attacks: These attacks involve some modification of the data stream or the creation of a false stream.

cryptographic attacks

Alice and Bob, fondly known as the first couple of cryptography.

Alice and Bob are recurring characters in science. They can sending messages to each other in secret. But no matter Alice’s and Bob’s thought-experiment scenario, there is always some sort of a communication problem at the core of it: they want to send a private message to each other without an interception (usually from Eve the eavesdropper). Because of these secret messages, Alice’s and Bob’s interactions are commonly used to frame questions about how information can transfer securely.Alice and Bob have a long history rooted in cryptography, the study of secure communications.

Types of Cryptography

Secret Key Cryptography (symmetric key)
Public Key Cryptography (asymmetric key)
Hash Functions

Secret Key Cryptography (symmetric key):-

Secret Key Cryptography

In symmetric key algorithms, both sender and receiver knows the the encryption and decryption keys. The encryption key is shared to receiver and the decryption key is calculated by him. In many cases, the encryption and decryption keys are the same.Symmetric Key Systems are faster and simpler but the problem is that sender and receiver have to somehow exchange key in a secure manner. The most popular symmetric key cryptography system is Data Encryption System(DES).

Examples:

AES
DES
Caesar Cipher

There are two basic building blocks of all encryption techniques: substitution and
transposition.

substitution Technique :

A substitution technique is one in which the letters of plaintext are replaced by other letters or by
numbers or symbols. If the plaintext is a sequence of bits, then substitution involves
replacing plaintext bit patterns with cipher text bit patterns.

Type of substitution technique-

Caesar Cipher
Monoalphabetic Cipher
Playfair Cipher
Hill Cipher
Polyalphabetic Cipher
One-Time Pad

Transposition Technique

All the techniques examined so far involve the substitution of a cipher text symbol
for a plaintext symbol. A very different kind of mapping is done with permutation on the plaintext letters. This technique is called as transposition cipher.

Type of transposition technique-

Rail Fence Cipher
Columnar Transposition Technique
Columnar Transposition Technique with Multiple Rounds
Book Cipher or Running Key Cipher.

Public Key Cryptography (asymmetric key):-

Public Key Cryptography

In public key cryptography, public key is used for encryption and a private key is used for decryption. Public key and Private Key are different. Here every one knows about public key used of encryption but private key is know to receiver only.

Examples:

ECC
Diffie-Hellman
DSS

Hash Functions

Public and private key cryptographic algorithms both involve transforming plaintext into ciphertext and then back into plaintext. By contrast, a hash function is one-way encryption algorithm. once you’ve encrypted your plaintext, you can’t ever recover it from the resulting ciphertext.