# Symmetric Key Cryptography | Cryptography Techniques

## Cryptography in Network Security-

In network security,

• Cryptography is a method of storing and transmitting data in a particular form.
• It ensures that only the person for whom the message is intended can read the message.

The message exchange using cryptography involves the following steps- ## Step-01:

At sender side,

• Using an encryption algorithm, the message is converted into an unreadable form.
• The message in unreadable form is called as cipher text.

## Step-02:

• The cipher text is sent to the receiver over the communication channel.
• Since the message is encrypted, the attackers can not read the message.

## Step-03:

• Using a decryption algorithm, the message is again converted into the readable form.
• Then, receiver can read the message.

## Cryptography Techniques-

Cryptography techniques may be classified as- 1. Symmetric Key Cryptography
2. Asymmetric Key Cryptography

In this article, we will discuss about symmetric key cryptography.

## Symmetric Key Cryptography-

In this technique,

• Both sender and receiver uses a common key to encrypt and decrypt the message.
• This secret key is known only to the sender and to the receiver.
• It is also called as secret key cryptography.

## Working-

The message exchange using symmetric key cryptography involves the following steps- • Before starting the communication, sender and receiver shares the secret key.
• This secret key is shared through some external means.
• At sender side, sender encrypts the message using his copy of the key.
• The cipher text is then sent to the receiver over the communication channel.
• At receiver side, receiver decrypts the cipher text using his copy of the key.
• After decryption, the message converts back into readable format.

## Symmetric Encryption Algorithms-

Some of the encryption algorithms that use symmetric key are-

• Advanced Encryption Standard (AES)
• Data Encryption Standard (DES)

The advantages of symmetric key algorithms are-

• They are efficient.
• They take less time to encrypt and decrypt the message.

## Point-01:

 The number of keys required is very large.

In symmetric key cryptography,

• Each pair of users require a unique secret key.
• If N people in the world wants to use this technique, then there needs to be N(N-1) / 2 secret keys.
• For 1 million people to communicate, a half billion secret keys would be needed.

### How N(N-1)/2 Keys Will Be Required?

• Consider a complete graph with N nodes.
• Consider each node represents one person.
• Then, each person will require (N-1) keys to communicate with other (N-1) people.
• Thus, each edge must have a unique key for communication.
• Thus, Number of keys required = Number of edges = nC2 = n(n-1)/2.

## Point-02:

• Sharing the secret key between the sender and receiver is an important issue.
• While sharing the key, attackers might intrude.

 To overcome this disadvantage, Diffie Hellman Key Exchange Algorithm is used for exchanging the secret key.

## Point-01:

In symmetric key cryptography,

• Both sender and receiver uses the same key.
• Sender encrypts the message using his copy of the key.
• Receiver decrypts the message using his copy of the key.
• The key must not be known to anyone else other than sender and receiver.
• If the secret key is known to any intruder, he could decrypt the message.

## Point-02:

• This cryptography technique is called as symmetric key cryptography.
• It is because both sender and receiver use the same key on their sides.

## Point-03:

• This cryptography technique is called as secret key cryptography.
• It is because the key has to be kept secret between the sender and receiver.

To gain better understanding about Symmetric Key Cryptography,

Watch this Video Lecture

Next Article- Asymmetric Key Cryptography | RSA Algorithm

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Summary Article Name
Symmetric Key Cryptography | Cryptography Techniques
Description
Cryptography in Network Security is a method of exchanging data in a particular form. Cryptography Techniques- Symmetric key cryptography and Asymmetric key cryptography. In symmetric key cryptography, sender and receiver use the same key for encryption and decryption.
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Gate Vidyalay
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