What is Symmetric Key Encryption? [An In-Depth Guide]

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What is Symmetric Encryption

What is Symmetric Key Encryption, and Why Does it Matter in the Modern World?

The internet works in mysterious ways. Behind one website, multiple components and parts are working together to get the users access to the page. One of these components is encryption, which essentially secures the connection between the user and the browser.

Today, people use symmetric encryption for a wide array of online functions and transactions. From paying for your order online to accessing your online account to talking to someone on Whatsapp, symmetric encryption has a role in ensuring your activities’ confidentiality and security.

This guide will explore what symmetric encryption is in detail, its benefits, the working mechanism, types of symmetric encryption, and much more. So, stay tuned.

What is Symmetric Encryption?

We know that encryption is like protecting some data or information from unauthorized access. In symmetric encryption, a key provides this protection, and users use the same key to decrypt the previously secured data.

So, just like a lock has one key for locking and unlocking, symmetric encryption requires one key for both encryption and decryption. Because we are talking about online transactions, users on both sides will have access to the same key. 

To clarify, let’s say that your friend has sent you a message over the web and secured it with an encryption key.

The encryption key will turn the text message into a cipher text for the time it is in transition. Once you receive the message at your end, your decryption key will decrypt it, allowing you to read it in plain text.

Because only the receiver and sender have access to the message or data secured with this method, people also refer to it as Symmetric Key Cryptography, secret key encryption, or private key cryptography.

How Does Symmetric Encryption Works?

In the text message example above, we have shared an overview of how encryption works. Let’s get into a bit more detail about how the symmetric encryption example works.

When an entity uses symmetric encryption and executes it, the process secures the shared plain text with a string of characters (including numbers & letters). After encrypting the plain text, the original message sent to the users will appear as a bunch of scrambled letters that make no sense.

The receiver also has the same cryptographic key as the sender. And they can utilize this key to decrypt the data or message. Hence, no one can read the data or message sent without the encryption key.

It looks simple, right? But it is not.

People have used symmetric encryption to secure almost everything on the web, which has proven successful. And this is not a new method. Instead, we can trace the origins of encryption to the era of Julius Caesar.

Yes, the shift cipher encryption, which inspired modern encryption standards, draws its roots from the Shift Cipher system used by Caesar.

What is Shift Cipher and How it Works?

Shift cipher is a substitution method in which another replaces the character you want to write with a fixed number of positions. If the number of substitutes is 5, the encryption process will replace the letter A with E, B with F, and so on.

So, let’s say you want to send “Hello” in cipher text. Here’s what the coded message will be;

Plain TextHELLO
Cipher TextLMQQS

So, HELLO converts to LMQQS. So, the person who knows the secret (substitution) will know how to decode the message.

However, this type of encryption won’t work today. That is why we have symmetric encryption to protect the volumes of information we share online.

Where is Symmetric Encryption Used?

Symmetric Encryption has a wide array of uses in different industries.

1. Banking

Banks have enabled online transactions for their customers. You might have seen PCI DSS written somewhere when making payments with the cards.

PCI DSS (Payment Card Industry Data Security Standard) includes a set of a dozen requirements that any business accepting credit card payments must comply with.

Within the PCI DSS requirements, one of the requirements is symmetric encryption, which aims to secure the credit card holder’s information.

2. Data Storage or Data at Rest

To secure the data stored on a cloud platform, one can use symmetric encryption for protection. This applies when the data is not being transferred. Another related concept is data at rest, which involves storing information on a server or a device.

Platforms like Google Docs, Dropbox, etc., store tremendous amounts of users’ data. Even our devices have much personal data we don’t want to send and save.

Henceforth, the solution we use to save such stored data is using symmetric encryption. For instance, CodeGuard (website backup tool) uses AES-256 bit strong encryption. Google Suite uses at-rest data encryption, and Microsoft Azure also uses symmetric encryption.

3. Website Security

Websites are open to the public, and they also collect user data and store their login information. All of this is confidential information that should not land in the wrong hands. Hence websites use symmetric key encryption to establish a secure connection between the user and the website server.

A website secured with symmetric encryption will display a small padlock and the “HTTPS” designation. Here the encryption works by designating a TLS/SSL certificate to the website.

Websites with this certificate authenticate servers, and they generate symmetric key algorithms for every session. Essentially the HTTPS system works via asymmetric encryption. But then, people use asymmetric encryption to exchange the symmetric keys for a TLS handshake.

So, when you browse a website, symmetric encryption will secure your interaction with the website.

This sums up the use of symmetric encryption and encapsulates most of our online activities.

Are Symmetric Keys Secure?

Yes, Symmetric key encryption is highly secure. We cannot use the word “unhackable” because there is a possibility that the calculation involved in the encryption can be reversed. But with the caveat attached, it can take thousands of years and several supercomputers working together to complete this process.

Didn’t understand? Well, here’s what we mean. At the time when encryption was being developed to its current state, several researchers and mathematicians were actively trying to find ways to secure communication between two entities over the web.

Now the web is a type of place where even when two people are talking, the third one is always listening. But researchers made encryption more robust and secure to ensure that this third entity does not access the data being transmitted.

Hence, researchers increased the length of the mathematical calculation that allows symmetric encryption to happen in the first place. And this becomes the first reason for the high security of symmetric encryption.

The randomness of the number included in the calculation forms the second factor. Since both the users, even in private key encryption, can choose different numbers to generate the same result, it adds to the security aspect because the third entity does not know the numbers added to the calculation.

Due to these two factors can take a long time to reverse the calculation and find the secret key to encrypt the communication, data, and transactions.

Types of Symmetric Encryption

For protection purposes, people can use different types of symmetric encryption methods.

1. Data Encryption Standard (DES): The DES standard, one of the oldest symmetric encryptions, is not used today. DES provided the users with three different sizes of encryption, including;

  • 64-bit
  • 128-bit
  • 192-bit

The numbers we see in bits represent the character length of the encryption key. Longer encryption keys are harder to crack. However, due to security issues, the DES standard has been phased out.

2. Triple Data Encryption Standard (3DES): The 3DES standard was built as a substitute for the DES standard and provided 3X protection. So, the 3DES system encrypts the plain text thrice. However, the 3DES system had some issues, leading to its successor, AES.

3. Advanced Encryption Standard (AES): The AES standard is a highly sophisticated security protocol. You will find that most online systems use this protocol for shielding data and storage. It is relatively more efficient and secure than the other types of symmetric encryption. The reason for its effectiveness lies in the different substitution methods, making the key generated with AES virtually impossible to crack.

Key Sharing | The Only Potential Defect in Symmetric Encryption

There are two issues with the key sharing system in symmetric encryption. And we need to share the keys in case the second entity to whom you are sending a message, etc., does not have access to the decryption key.

1. Key Exhaustion: This phenomenon happens when some information about the encryption key leaks after it is shared. So, if an attacker is constantly trying to hack into the encryption standard, eventually, they will have enough information to crack the key.

A way around this is using the key hierarchy system. This will ensure that the encryption key or keys are not overused and that there is an appropriate rotation of the keys. Hence, effective key management is required. 

2. Attribution Data: In symmetric encryption algorithms, there is no way to identify the purpose of the key. In other words, we cannot determine what information is bound to the particular key. While there is a system to record this information in asymmetric encryption, there isn’t one here.

Learn more about the difference between Symmetric vs Asymmetric Encryption

Symmetric Key Encryption FAQs

1. What is meant by symmetric key encryption?

Symmetric key encryption is a type of encryption that employs the same key for encrypting and decrypting the data in transit. So both the sender and the recipient have identical copies of the key.

2. What is the difference between symmetric and asymmetric key encryption?

In symmetric encryption, the only key is used for encryption and decryption, whereas in asymmetric encryption, two different keys are used for encryption and decryption.

3. What is a symmetric key example?

Symmetric key encryption is used in payment applications, where PII needs to be secured in order to prevent identity theft or fraud charges.

4. Is AES symmetric or asymmetric?

AES stands for Advanced Encryption Standard and is one of the commonly used symmetric key encryption.

Conclusion of What is Symmetric Key Encryption

Symmetric key encryption is a highly useful, popular, and effective method of securing data and information. It is widely used in the web world and is considered virtually unbreakable. With time, the usability and applications of this encryption standard will only increase. However, it is also essential to build an effective key management system. This will address the couple of loopholes we have discussed above and make symmetric encryption even better.

Janki Mehta

Janki Mehta

Janki Mehta is a Cyber-Security Enthusiast who constantly updates herself with new advancements in the Web/Cyber Security niche. Along with theoretical knowledge, she also implements her practical expertise in day-to-day tasks and helps others to protect themselves from threats.