All You Need to Know About Symmetric Encryption

With this era of encryption of digital assets taking huge strides this past decade, it has become essential to understand what symmetric encryption is, and why it is necessary. Arguably the most simple encryption category, it is still widely used today for multiple crucial purposes, which you will look into in more detail.

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What is Cryptography?

Cryptography is the science of encrypting and decrypting data to prevent unauthorized access. Encryption is the process of making the plaintext unreadable to any third party, which generates the ciphertext. Decryption is the process of reversing the encrypted text to its original readable format, i.e., plaintext.


There are two types of encryption in cryptography: 

  1. Symmetric Encryption
  2. Asymmetric Encryption

Today we are going to focus on what is symmetric encryption.

What is Symmetric Encryption?


Symmetric Encryption algorithm relies on a single key for encryption and decryption of information. Both the sender and receiver of the message need to have a pre-shared secret key that they will use to convert the plaintext into ciphertext and vice versa.

As shown below in the figure, the key which is being used for encrypting the original message is decrypting the ciphertext. The key must be kept private and be known only to the sender and the receiver.


For example, if Paul wants to send a simple message to Jane, they need to have a single encryption key that both of them must keep secret to prevent snooping by malicious actors. If the message “I am ready” is converted to ciphertext using a specific substitution cipher by Paul, Jane must be aware of the substitution shift to decrypt the ciphertext once it reaches her.

To sum it up, the entire process will be as shown below:

  • Step 1: Paul and Jane decide on a common key to be used

  • Step 2: Paul sends the secret encryption key to Jane or vice versa

  • Step 3: Paul uses the private key to encrypt the original message

  • Step 4: Paul sends the encrypted message to Jane

  • Step 5: Jane uses the secret key to decrypt the message that was already present with her

Following the above process, Paul and Jane communicate privately without the fear of anyone lurking on the route. Since only both of them have the secret key needed to encrypt and decrypt the message, no third party who can intercept the encrypted message can break into it.

Now that you have a foundation, it’s time to walk you through its applications.

Where is Symmetric Key Cryptography Used?

Symmetric encryption is essential for many day-to-day activities on the internet, ranging from safe online browsing to banking applications. Some of these applications are as follows- 


  • Payment Applications:

Many online banking and payment applications require the verification of personally identifiable information before proceeding with their transactions. It helps in predicting the correct information to prevent fraudulent activities and cybercrime.

  • Securing Data at Rest:

When a website or organization stores personal information regarding their users or the company itself, it is protected using Symmetric encryption. This is done to prevent all kinds of snooping from either outside hackers or disgruntled employees inside the office, looking to steal crucial information.

  • SSL/TLS Handshake:

Symmetric encryption plays a significant role in verifying website server authenticity, exchanging the necessary encryption keys required, and generating a session using those keys to ensure maximum security, instead of the rather insecure HTTP website format.

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Why is Symmetric Key Cryptography Called Private Key Cryptography?

With the entire architecture of Symmetric Cryptography depending on the single key being used, you can understand why it’s of paramount importance to keep the key secret on all occasions. If the sender somehow transmits the secret key along with the ciphertext, anyone can intercept the package and access the information. Consequently, this encryption category is termed private key cryptography, since a big part of the data’s integrity is riding on the promise that the users can keep the keys secret.

Provided you manage to keep the keys secret, you still have to choose what kind of ciphers you want to use to encrypt the information. In symmetric-key cryptography, there are broadly two categories of ciphers that you can employ. Have a look at what they are in the following section.

What Are the Types of Ciphers Being Used?

Two types of ciphers can be used in symmetric algorithms. These two types are:

  • Stream Ciphers

  • Block Ciphers

1. Stream Ciphers

Stream ciphers are the algorithms that encrypt basic information, one byte/bit at a time. You use a bitstream generation algorithm to create a binary key and encrypt the plaintext.

The process for encryption and decryption using stream ciphers are as follows :

  • Get the plaintext to be encrypted.

  • Create a binary key using the bitstream generation algorithm.

  • Perform XOR operation on the plaintext using the generated binary key.

  • The output becomes the ciphertext.

  • Perform XOR operations on the ciphertext using the same key to get back the plaintext.


The most well-known stream ciphers are RC-4, SALSA and PANAMA.

2. Block Ciphers

On the other hand, block ciphers dissect the raw information into chunks of data of a fixed size. The size depends on the exact cipher being used. A 128-bit block cipher will break the plaintext into blocks of 128-bit each and encrypt those blocks instead of a single digit. These ciphers are slower but much more tamper-proof and are used in some of the most common algorithms being employed today.



Today, the most popular symmetric-key algorithms like AES, DES, and 3DES are block cipher methodology subsets. 

What are the Advantages of Using Symmetric Key Cryptography?

Symmetric encryption has a few advantages over its counterpart, asymmetric encryption, which uses two different keys to encrypt and decrypt data. Some of these advantages are -


  • Faster than Asymmetric: Symmetric encryption is relatively quicker than asymmetric encryption. Using a single key for both encryption and decryption makes it comparatively less complex.
  • Better Performance: Symmetric Encryption has been found to have a higher performance metric when compared to asymmetric encryption. Fewer calculations help in the better memory management of the host.
  • Better Optimization: Bulk amounts of data that need to be encrypted are very well suited for symmetric algorithms. Since they are much quicker, handling large amounts of data is simple and easy to use in servers and data farms.
  • Easy Implementation: With only a single key needed for both encryption and decryption of data, setting up symmetric infrastructure for an organization is relatively easy compared to asymmetric encryption.

This brings an end to this tutorial on symmetric-key cryptography.

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How Can Simplilearn Help You?

By now you would have understood the importance of symmetric key cryptography in today’s internet sphere and its value in safeguarding our privacy and security. With many bases to cover in the world of cybersecurity, cryptography is one of the most crucial concepts, even though there are multiple more topics essential to excel as a cybersecurity expert.

Simplilearn offers a Post Graduate Program In Full Stack Web Development course designed to equip you with all the skills necessary to start or promote your career in cybersecurity. It doesn’t have any academic pre-requirements, and the introductory module will prepare beginners for the course ahead. Training for highly sought-after certifications like CompTIA Security+, CEH, CISM, and CISSP are at the forefront of this course, preparing you for the best jobs being offered in the industry.


You started with this tutorial by getting a small revision on cryptography, learned about symmetric encryption, its various applications, and its advantages, all the way up to the types of ciphers used in this category of encryption. Hope it comes of value to you. 

If you have any questions, feel free to ask us in the comment section below. Our team of experts will answer them for you, at the earliest!

About the Author

Ravikiran A SRavikiran A S

Ravikiran A S works with Simplilearn as a Research Analyst. He an enthusiastic geek always in the hunt to learn the latest technologies. He is proficient with Java Programming Language, Big Data, and powerful Big Data Frameworks like Apache Hadoop and Apache Spark.

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