# Cryptography

## What is Cryptography?

The word cryptography is the combination of the words crypto and graphy, where crypt means secretive or hidden while graphy means written stuff. So, one can define cryptography as the art of hiding data for securing the same. This promotes the prevention of accessing the information at the unauthorized level.

One should note here the mathematical concepts that are known as algorithms, convert the information into one that can only be understood by the authorized level.

Cryptography is associated with encryption and decryption as encryption and decryption are the techniques of cryptography.

### Basics of Cryptography

Data is quite confidential stuff. When it is available in a form that anyone can read and understand it without applying special means then such a form is known as plaintext or cleartext. However, when it is converted into a disguised form in order to hide it is referred to as encryption. The encrypted information or data is called ciphertext.

Through encryption, data can be hidden from the ones to which it does not belong. However, the indented user must have to change the ciphertext again into plain text and this process is regarded as decryption. This is clearly shown in the figure shown above.

Basically, the science that allows the information to get encrypted or decrypted uses mathematics in the form of algorithms so that sensitive information can be transmitted over an insecure network such as the internet. This sensitive information will then be accessed only by the respective user.

There is one more terminology that is quite famous relative to cryptography which is called cryptanalysis which refers to analyzing and decoding secured communication. In order to achieve this, the idea of analytical reasoning, some mathematical tools, pattern findings along with determination and luck is necessary. The ones that perform cryptanalysis are called cryptanalysts, generally regarded as attackers.

### Primary Characteristics of Cryptography

The following are the main features associated with cryptography:

1. Security: It allows the information to get accessed only by the user or recipient to which it belongs as no other individual can access it.
2. Non-repudiation: The word repudiation is associated with the act of refusal of something by someone. Basically, here it is concerned with the fact that the one who has sent the data cannot deny the sent information at the later levels of the communication.
3. Integrity: This technique promotes maintaining the uniqueness of the sent information as the data cannot be modified while transmitting or when present in storage for transition. However, if one intends to add the information then will be going to be visible that changes have been made.
4. Authentication: The recipients involved in the communication i.e., the sender and receiver cannot change their identities during communication. Not only this the destination where the data is to be delivered is also verified and is unchangeable.

## How Cryptography Works?

Till now we have got the idea of basic terminologies like plain and ciphertext along with encryption and decryption. We have understood that cryptographic algorithm is basically mathematical function that allows the processes like encryption and decryption to take place. Basically, the algorithm constitutes the combination of word, number or phrase that jointly converts plaintext into ciphertext.

One should note here that a single plaintext can be converted into different ciphertexts when different keys are involved. The level of security which the encrypted information holds shows dependency on the strength of the cryptographic algorithm and the confidentiality of the keys involved.

A cryptosystem is a system that is constituted by a cryptographic algorithm along with all possible keys and the protocols through which it works. Thus, the main components of the cryptosystem are:

• Plaintext
• Encryption Algorithm
• Encryption key
• Ciphertext
• Decryption Algorithm
• Decryption key

If we talk about conventional cryptography that is also known as symmetric-key encryption, then in a single key is used for encryption as well as decryption. DES which stands for Data Encryption Standard is one of the examples of conventional cryptosystem and is very much used by the US government.g

### Types of Cryptography

The following are the types of cryptography:

1. Symmetric Key Cryptography: It is sometimes referred to as a Secret key or conventional cryptography. This technique of cryptography is the one where there is a single set of keys used by the sender and receiver for the purpose of encryption and decryption. The key about which we are talking here is the piece of information or the parameter used to determine the functional orientation of the algorithm.

One of its crucial parameters is that the key used in the algorithm must be known to each and every recipients that are involved otherwise the decryption will not be possible.

This approach of cryptography is simple and fast to achieve however, secured key exchange is quite necessary here as this is important for decryption to take place. Here key plays a crucial role and its secrecy maintenance is quite an important task.

2. Asymmetric Key Cryptography: This is different from the one which is discussed above in a way that here two unique keys are used out of which one is private while the other is public. The two are used in a way that encryption is performed using the public key and at the time of decryption private key is used. Another name given to this type is public key cryptography which is quite an advanced method.

DSS which is a digital signature standard is an algorithm invented by the NSA for the authentic purpose of electronic documents.