## What is Cryptosystems?

A cryptosystem is also called a cypher system. It implements cryptographic techniques using various cryptographic components such as plain text, encryption algorithm, cypher text, decryption algorithm, and encryption key to provide information security services. There are two types of a cryptosystem, such as Symmetric Key Encryption and Asymmetric Key Encryption.

You can see the sender want to send a message to a receiver secretly, without revealing it to any third party in the above diagram. To accomplish that, the cryptosystem comes into the picture. At the sender system, the cryptosystem takes the sender Message i. Plain text and using a secret key (encryption key) it performs some encryption algorithm, forms a ciphertext, and then sends it to the receiver. After receiving ciphertext at the receiver side cryptosystem perform decryption algorithms using a secret key (decryption key) and convert cipher text into plain text. The cryptosystem’s goal is to send private data from sender to receiver without interpretation of any third party.

### Components of Cryptosystem

Let us discuss some of the components below.

#### 1) Plain text

The plain text is a message or data which can understand by anyone.

#### 2) Ciphertext

The ciphertext is a message or data that is not readable; it is accomplished by performing the encryption algorithm on plain text using an encryption key.

#### 3) Encryption Algorithm

It is a process of converting plain text into Ciphertext using an encryption key. It takes two inputs, i.e. plain text and encryption key, to produce ciphertext.

#### 4) Decryption Algorithm

It is an opposite process of an encryption algorithm; it converts cipher text into plain text using the decryption key. It takes two inputs, i.e. ciphertext and decryption key, to produce plain text.

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#### 5) Encryption Key

It is a key which sender used to convert plain text into ciphertext.

#### 6) Decryption Key

It is a Key which the receiver uses to convert ciphertext into plain text.

### Types of Cryptosystems

There are two types of Cryptosystems – Symmetric Key encryption and Asymmetric key encryption. Let’s Discuss these two types in detail.

#### 1) Symmetric Key Encryption

- In symmetric key encryption, both the sender and the receiver use the same secret key, i.e. encryption key, to perform encryption and decryption. Symmetric key encryption is also known as symmetric cryptography.
- Some algorithms use symmetric key concepts to achieve security. For example, DES (Data Encryption Standard), IDEA (International Data Encryption Algorithm), 3DES (Triple Data Encryption Standard), Blowfish.
- All cryptosystems mostly use symmetric key encryption.
- In Symmetric-key encryption, the sender and receiver agree on the same secret key. The sender encrypts the private data, i.e. plain text, using a secret key and sends it to the receiver. After receiving data, the receiver uses the same secret key, which the sender uses to encrypt data. Using this secret key, it converts cipher text into plain text.

In the below picture, we can see the working of Symmetric key encryption.

**Features of cryptosystem in case of Symmetric-key encryption:-**

- As they use the same key for encryption and decryption, they have to share that secret key.
- To prevent any type of attack, a secret key needs to updated at regular interval of time.
- The length of the secret key in symmetric key encryption is small; hence, encryption and decryption are faster.
- There must be a mechanism to share a secret key between the sender and receiver.

**Challenges for symmetric key encryption-**

**Generating secret key:**To share the Secret key, both the sender and the receiver need to agree on the symmetric key, which requires a key generation mechanism in place.**Trust issue:**There must be trust between the sender and the receiver as they share the symmetric key. E.g. suppose the receiver lost his secret key to attackers, and he does not inform to the sender.

#### 2) Asymmetric key encryption

In asymmetric key encryption, two different keys are used by the sender and the receiver for encryption and decryption processes. Asymmetric key encryption is also known as public-key encryption.

In the above picture, we can see how asymmetric key encryption works.

- In asymmetric key encryption, two keys are used. i.e. public key and private key. These two keys are related to each other in a mathematics way. A public key is stored in a public repository, and private keys are stored in a private repository.
- Using the receiver public key sender encrypt the private data and send it to the receiver. After receiving private data, the receiver uses his private to decrypt private data.
- The length of keys in asymmetric key encryption is large; hence encryption and decryption processes in asymmetric key encryption become slow compared to symmetric key encryption.
- Calculating the private key based on the public key is computationally not so easy. As a result, public keys can be freely shared, allowing users to easily and conveniently encrypt content and verify digital signatures, and private keys can be kept secret, making sure that content can be decrypted and private key owners can only create digital signatures. Asymmetric key cryptosystems face the challenge, i.e. the user must be confident that the public key he is using for transmission with an individual is really that person’s public key and was not handled by an attacker.
- Also, because public keys need to be shared, these public keys are large in size; hence, they are difficult to remember, so they are stored on digital certificates for secure transmission and sharing. While private keys cannot be shared, they are simply stored in the cloud software or operating system you are using or on hardware devices. Many internet protocols like SSH, OpenPGP, SSL/TLS used in asymmetric cryptography for encryption and digital signature functions.

### Conclusion

This article has seen how cryptosystem helps encrypt and decrypt messages securely and conveniently.

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