Symmetric vs. Asymmetric Encryption: What are the differences?

Updated on July 18, 2023
Symmetric vs. Asymmetric Encryption: What are the differences?

Encryption is how we keep data private in an increasingly digital world. Whether you’re trying to protect your personal files, communications, or business data, understanding encryption methods is key. The two main types are symmetric encryption, where the same key is used to encrypt and decrypt data, and asymmetric encryption, which uses a public key to encrypt data and a private key to decrypt it. Both have a role to play in data security, so let’s dive in and explore how they work, their pros and cons, and how you can use them to protect your own information. By the end of this article, you’ll have a solid understanding of the differences between these two foundational encryption techniques.

What Is Symmetric Key Encryption?

What Is Symmetric Key Encryption?

Symmetric encryption uses a single key to both encrypt and decrypt data. This means the same key is used by both the sender and recipient.

The main benefit of symmetric encryption is that it’s fast. It’s ideal for encrypting large amounts of data. The downside is that you have to share the key with the recipient in a secure way. If the key is compromised, anyone can access the encrypted data.

Some common examples of symmetric encryption algorithms are:

  • AES (Advanced Encryption Standard)
  • Blowfish
  • RC4

Symmetric encryption is best used when speed and efficiency matter and when a secure key exchange system is in place. For most people, symmetric encryption may be tricky to implement effectively due to the key sharing challenge.

Common Symmetric Encryption Algorithms

With symmetric encryption, the same key is used to encrypt and decrypt the data. This includes algorithms like:

  • AES (Advanced Encryption Standard) – The most commonly used algorithm. Fast and secure for encrypting files, disks, and network connections.
  • DES (Data Encryption Standard) – An older algorithm that uses a 56-bit key. Not the most secure, but still used in legacy systems.
  • 3DES – Uses three rounds of DES encryption with different keys to increase security. Also still used in older systems.
  • Blowfish– A fast, public domain algorithm suitable for applications where the key does not change often.
  • RC4 -A stream cipher used in popular protocols like Secure Sockets Layer (SSL) to protect Internet traffic.

Symmetric encryption is fast and efficient, but the big downside is that you must securely share the key with anyone who needs to decrypt the data. For now, remember that if you need to quickly encrypt data where security and speed matter, symmetric encryption and the AES algorithm are probably your best friends.

What Is Asymmetric Key Encryption?

What Is Asymmetric Key Encryption?

Asymmetric encryption is more computationally intensive than symmetric encryption, so it is often used to encrypt a symmetric key which is then used to encrypt bulk data. This combines the efficiency of symmetric encryption with the security of asymmetric encryption.

Asymmetric encryption uses two separate keys for encrypting and decrypting data. There is a public key and a private key. The public key can be shared with anyone and is used to encrypt messages. The private key is kept secret and is used to decrypt messages that were encrypted with the public key.

Because the public key cannot decrypt messages that were encrypted with it and the private key is kept secret, this method is very secure. Asymmetric encryption is often used when communicating over the internet or storing sensitive data in the cloud, where public keys can be exchanged to facilitate secure communication.

Anyone with the public key can encrypt data that can only be decrypted by the holder of the private key. This also allows for digital signatures because data encrypted with the private key can be decrypted with the public key, proving that the message is authentic.

Common Asymmetric Encryption Algorithms


Common Asymmetric Encryption Algorithms RSA

RSA is one of the first public-key cryptosystems and is still widely used today. It utilizes a public key and a private key. The public key can be shared with anyone, while the private key must be kept secret. RSA works by generating two large prime numbers to create a public key and a private key. The public key is used to encrypt messages and the private key is used to decrypt them.


Common Asymmetric Encryption Algorithms ECC

Elliptic curve cryptography (ECC) uses algebraic curves over finite fields to generate public and private keys. ECC uses smaller keys than RSA to provide the same security level. This results in faster computations, lower power consumption, as well as memory and bandwidth savings. ECC is a popular choice for constrained environments like mobile devices.


Symmetric vs. Asymmetric Encryption

The Diffie-Hellman key exchange method allows two parties to establish a shared secret key over an insecure channel. It enables two parties to agree upon a secret key without any prior knowledge and without exchanging any secret information over the channel. Diffie-Hellman is used in many internet security protocols like SSH, IPsec, SSL, and TLS.

By using a combination of these algorithms, we can build secure communication systems.

When to Use Symmetric vs. Asymmetric Encryption?

When Speed and Efficiency Matter Most

Use symmetric encryption when you need to encrypt large amounts of data quickly and decrypt it efficiently. Things like:

  • Encrypting files on a USB drive
  • Protecting data in transit over a network
  • Securing communications in messaging apps

Symmetric encryption uses a single secret key to both encrypt and decrypt data. This makes it fast since the same algorithm is used for encryption and decryption. The downside is that the secret key must be shared between the sender and recipient, which requires a secure key exchange method.

For Ultimate Security

Choose asymmetric encryption when security is your top priority. Some examples:

  • Encrypting sensitive data like credit card numbers
  • Securing government and healthcare records
  • Protecting intellectual property

Asymmetric encryption uses a public key to encrypt data and a private key to decrypt it. However, asymmetric encryption is significantly slower and cannot efficiently encrypt large amounts of data.

A hybrid solution

For most everyday encryption needs, a hybrid solution using both symmetric and asymmetric encryption works well. Asymmetric encryption is used to securely exchange a symmetric key, then symmetric encryption is used for the actual data encryption due to its speed and efficiency. This provides the perfect balance of security and performance.

Symmetric Vs Asymmetric Encryption

Symmetric and asymmetric encryption are two of the most common types of cryptography.

Symmetric encryptionAsymmetric encryption
Symmetric encryption uses the same key for both encryption and decryption. This single key must be shared between the sender and receiver before any data can be exchanged.Asymmetric encryption uses two separate keys for encryption and decryption. One key is public and can be shared with anyone. The other key is private. Anything encrypted with the public key can only be decrypted using the private key.
Symmetric encryption tends to be faster than asymmetric, but sharing secret keys can be tricky.Asymmetric encryption solves this problem since the public key can be distributed openly, and anything encrypted with it can only be read by the holder of the private key.
Symmetric algorithms like AES and DES are faster and less resource-intensive.Asymmetric algorithms like RSA and ECC are slower but more secure.
Symmetric encryption is best for bulk encryption of data.Asymmetric encryption is ideal for encrypting small amounts of data, like encryption keys.
Symmetric encryption is a simple, fast solution ideal for bulk data.Asymmetric encryption is a secure, scalable option best for managing keys and small data amounts.

Examples of Symmetric Encryption

Symmetric encryption is best for encrypting data where both the sender and receiver can access the key, such as storing data on a local drive or flash drive.

Public key encryption is typically better for communication over the Internet since it solves the problem of securely exchanging the keys.

Examples of Asymmetric Encryption

Asymmetric encryption allows for secure communication over the internet because the public key can be openly shared while the private key remains secret. This allows two parties who have never met before to communicate securely.

Does Astrill VPN use symmetric or asymmetric encryption?

Astrill VPN uses symmetric and asymmetric encryption to protect users’ data and ensure privacy.

Symmetric Encryption

Astrill VPN uses strong 256-bit AES symmetric encryption to encrypt all data between your device and Astrill’s servers. AES is a robust cipher that would take an impractical amount of time to crack. Your data and activity are hidden from anyone trying to snoop on your connection.

Asymmetric Encryption

Astrill VPN uses asymmetric encryption like 2048-bit RSA and Diffie-Hellman for key exchange and authentication. Asymmetric encryption allows keys to be exchanged over the public internet without compromising security. Your private key is kept secure on your device, while your public key can be shared. This dual encryption approach is considered very secure.

The Best of Both Worlds

Astrill VPN provides fast, secure encryption and authentication by combining symmetric and asymmetric encryption. Symmetric encryption quickly encrypts your data traffic, while asymmetric encryption securely handles key exchange and login credentials. This hybrid model gives you the best speed and security in one VPN solution.


Got questions about symmetric vs. asymmetric encryption? Here are some common ones:

Q: What encryption algorithm is not symmetric?

Asymmetric encryption like RSA and ECC are not symmetric. They use different keys to encrypt and decrypt data.

Q: Is VPN symmetric or asymmetric?

VPNs typically use asymmetric encryption to establish a secure connection and exchange keys, then use symmetric encryption for the actual data transfer due to its speed.

Q: What’s the main difference between the two?

Symmetric encryption uses the same key to encrypt and decrypt data, while asymmetric encryption uses different keys. Asymmetric is slower but better for key exchange.


At the end of the day, for most of your basic needs, symmetric encryption works just fine and dandy. But if you need to securely share information or verify someone’s identity, asymmetric encryption is the way to go. The differences between the two come down to a balancing act between speed and security. Choose the option that meets your needs, implement it properly, and your data will be locked up tight.

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About The Author

Bisma Farrukh

Bisma is a seasoned writer passionate about topics like cybersecurity, privacy and data breach issues. She has been working in VPN industry for more than 5 years now and loves to talk about security issues. She loves to explore the books and travel guides in her leisure time.

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