# Cryptography in Computer Network

**Cryptography**: Cryptography is derived from the Greek word, which means "Hidden Secrets." In other words, it is an art in which we can protect our data and information. Through cryptography, we convert our data into Unreadable Secret Codes, called Cipher Text and can read this data only, which will have the secret key to decrypt it. Decrypt data is called plain text. It maintains the security and integrity of the data.

In cryptography, encryption and decryption are two processes. It is used to protect the Messages, Credit/Debit Card details, and other relevant information. In encryption, plain text is converted to ciphertext, and in decryption, the ciphertext is converted to plain text.

Cryptography has many advantages because encryption makes your data completely secure and safe. After encrypting the data, even if it is hacked or stolen, no one can access or read your data.

**Working**

When you send a message using an encrypted messaging service, this service converts the message into code. After this, only the right user can read this message. Digital encryption is highly complex, so it is difficult to crack.

### Encryption

In cryptography, encryption is a process in which the information is converted into a secret code called ciphertext. Ciphertext cannot be easily understood, only experts can understand it. The main purpose of encryption is to secure digital data or information, which transmit via the internet.

### Decryption

Decryption is a process in which encrypted data is converted back to original data. The encrypted data is called ciphertext, and the original data is called plain text, and the conversion of ciphertext to plain text is called decryption.

### Types of Keys

There are used three different types of the key in cryptography: a secret key, public key, and private key. The secret key is used in the symmetric-key cryptography, and the other two keys is used in the asymmetric key cryptography, as shown in the figure.

There are two types of cryptography

- Symmetric key cryptography
- Asymmetric key cryptography

### Symmetric key cryptography

Symmetric key cryptography is that cryptography in which the same key (only one key) is used for encryption of plain text and decryption of ciphertext. Symmetric key cryptography is also known as secret-key cryptography.

### Asymmetric key cryptography

Asymmetric key cryptography is that cryptography in which both encryption and decryption have different keys. In this, the public key is used to do encryption, and the private key is used to do the decryption. It is also called public-key cryptography.

**For example**, if Paul sends a message to bob, they will use the bob's public key to encrypt the message, and then bob will decrypt that message with their private key.