PRINCIPLE OF CRYPTOGRAPHY

Basic Concept Cryptography

Cryptography is a method of using advanced mathematical principles in storing and transmitting data in a particular form so that only those whom it is intended for can read and process it.

Cryptography Terms

Encryption: It is the process of locking up information using cryptography. Information that has been locked this way is encrypted.

Decryption: The process of unlocking the encrypted information using cryptographic techniques.

Key: A secret like a password used to encrypt and decrypt information. There are a few different types of keys used in cryptography.

Steganography: It is actually the science of hiding information from people who would snoop on you.

The Basic Principles

1. Encryption

In a simplest form, encryption is to convert the data in some unreadable form. This helps in protecting the privacy while sending the data from sender to receiver. On the receiver side, the data can be decrypted and can be brought back to its original form. The reverse of encryption is called decryption. 

2. Authentication

This is another important principle of cryptography. In a layman’s term, authentication ensures that the message originated from the originator claimed in the message. Authentication is the process of recognizing a user’s identity.

3. Integrity

This means that Cryptography should ensure that the messages that are received by the receiver are not altered anywhere on the communication path. 

4. Non Repudiation

Assurance that the sender of information is provided with proof of delivery and the recipient is provided with proof of the sender's identity, so neither can later deny having processed the information.

Types of Cryptography

There are two types of cryptography techniques :

• Secret key Cryptography
• Public key cryptography

1. Secret Key Cryptography(Symmetric Encryption)

This type of cryptography technique uses just a single key. 

The sender applies a key to encrypt a message while the receiver applies the same key to decrypt the message. 

Since only a single key is used, we say that this is a symmetric encryption.

A cryptographic key is a string of bits used by a cryptographic algorithm to transform plain text into cipher text or vice versa.

The biggest problem with this technique is the distribution of keys as this algorithm makes use of a single key for encryption or decryption.

This is the simplest kind of encryption that involves only one secret key to cipher and decipher information.

Symmetrical encryption is an old and best-known technique. It uses a secret key that can either be a number, a word or a string of random letters.

It is blended with the plain text of a message to change the content in a particular way.

The sender and the recipient should know the secret key that is used to encrypt and decrypt all the messages. AES, DES, RC5, and RC6 are examples of symmetric encryption.

The most widely used symmetric algorithm is AES-128, AES-192, and AES-256.

The main disadvantage of the symmetric key encryption is that all parties involved have to exchange the key used to encrypt the data before they can decrypt it.

2. Public Key Cryptography(Asymmetric Cryptography)

This type of cryptography technique involves two key crypto systems in which a secure communication can take place between receiver and sender over an insecure communication channel. 

Since a pair of keys is applied here, this technique is also known as asymmetric encryption.

In this method, each party has a private key and a public key. The private key is secret and is not revealed while the public key is shared with all those whom you want to communicate with. 

If Alice wants to send a message to Bob, then Alice will encrypt it with Bob’s public key and Bob can decrypt the message with its private key.

Asymmetric encryption uses two keys to encrypt a plain text.Secret keys are exchanged over the Internet or a large network. 

It ensures that malicious persons do not misuse the keys.

It is important to note that anyone with a secret key can decrypt the message and this is why asymmetric encryption uses two related keys to boosting security.

A public key is made freely available to anyone who might want to send you a message. The second private key is kept a secret so that you can only know.

A message that is encrypted using a public key can only be decrypted using a private key, while also, a message encrypted using a private key can be decrypted using a public key.

Security of the public key is not required because it is publicly available and can be passed over the internet. Asymmetric key has a far better power in ensuring the security of information transmitted during communication.

Asymmetric encryption is mostly used in day-to-day communication channels, especially over the Internet.

Popular asymmetric key encryption algorithm includes RSA, DSA etc