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.

Symmetric encryption is a type of encryption used today. It is used in 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 to play in ensuring the confidentiality and security of your activities.

This guide will explore what is symmetric encryption in details, 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. Now in symmetric encryption, this protection is provided by a key, and the same key is used to decrypt the data secured before.

So, consider that a lock has one key to lock and unlock; similarly, in symmetric encryption, one key is required to encrypt & decrypt. 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 the message is received at your end, your decryption key will decrypt it, and you can read it in plain text.

Because only the receiver and sender have access to the message or data secured with this method, it is also called 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 symmetric encryption example works.

When an entity uses symmetric encryption and executes it, the plain text shared is secured with a string of characters (including numbers & letters.). After the plain text is encrypted, the original message sent to the users will look like 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.

Looks simple, right? But it is not.

Symmetric encryption has been used to secure almost everything on the web and has proven to be a successful method. 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 has helped form the modern encryption standards, was inspired by the Shift Cipher system used by Caesar.

What is Shift Cipher and How it Works?

Shift cipher is a substitution method in which the character you want to write is replaced by another by a fixed number of positions. If the number of substitutes is 5, the letter A will be replaced by E, B will be replaced by 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, symmetric encryption is one of those requirements and it is added to secure the credit card holder’s information.

2. Data Storage or Data at Rest: For securing the data stored on a cloud platform, symmetric encryption can be used to protect the same. This is when the data is not being transferred. Another concept related to data storage is data at rest when information is stored 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 solutions 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 all public and they also collect data of the users along with storing 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 that has been secured with symmetric encryption will have a small padlock and the “HTTPS” designation. Here the encryption works by designating a TLS/SSL certificate to the website.

Websites with this certificate have authenticated servers, and symmetric key algorithms are generated for every session. Essentially the HTTPS system works via asymmetric encryption. But the, asymmetric encryption is used for exchanging the symmetric keys for a TLS handshake.

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

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

Are Symmetric Keys Secure?

Yes, Symmetric key encryption is highly secure. We cannot use the word unhackable, as there is a possibility that the calculation that goes into 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 trying to find a way to secure the 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 to ensure that this third entity does not get the data being transmitted, encryption was made more robust and secure.

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

The second factor is the randomness of the number included in the calculation. 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 into the calculation.

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

Types of Symmetric Encryption

Different types of symmetric encryption methods can be used for the protection purposes.

1. Data Encryption Standard (DES): The DES standard is one of the oldest symmetric encryptions and 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, the DES standard has been phased out due to security issues.

2. Triple Data Encryption Standard (3DES): The 3DES standard was built as a substitute for the DES standard and provided 3X protection. So, the plain text in the 3DES system gets encrypted thrice. Still, the 3DES system was riddled with some issues, giving way to its successor, AES.

3. Advanced Encryption Standard (AES): The AES standard is a highly sophisticated security protocol. You will find that most of the online systems are using 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 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.