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VPN Encryption Explained: How Does a VPN Encrypt Your Data?

vpn encryption

For most VPN users, VPN encryption is a complex and uninteresting topic. As long as their VPN software ensures that all of their data is protected and private, they don’t want to understand how readable information is turned into encrypted and protected data. That said, this is a very interesting topic that every privacy enthusiast should know more about, as it will help them better understand how VPN services work.

In this guide, we’ll delve into the intricacies of VPN encryption, demystifying the underlying concepts and technologies involved. We’ll discuss how VPN encryption works, the various encryption protocols and ciphers utilized, and their strengths and weaknesses. Read on to learn everything you should know about VPN encryption.

Why is VPN Encryption Important?

VPN Encrypted Data

VPN encryption is important because it protects your identity by ensuring that your online activities remain private and secure. By encrypting your Internet traffic, VPN services make it difficult for anyone, including government agencies or hackers, to monitor or track your online behavior. If anyone intercepts your encrypted traffic, they won’t be able to see the content of the transmitted data.

What’s more, when a VPN routes your traffic through its encrypted tunnel, even Internet Service Providers won’t be able to see your VPN-encrypted connection. The VPN prevents ISPs from logging your data and selling it to advertisers. Even if you have a trustworthy Internet Service Provider, it’s always better to run your Internet connection through a VPN tunnel than to use apps and web browsers without any network protection.

The encryption transforms your data into an unreadable format. This makes it nearly impossible for unauthorized individuals to intercept, access, or decipher your sensitive information, such as passwords, financial details, or personal data.

Having a secure connection is particularly valuable when using public Wi-Fi networks. These networks are often prone to security risks, as cybercriminals may attempt to intercept data transmitted over them. With VPN encryption, your data is protected from eavesdropping and potential attacks, ensuring the safety of your information.

By serving as the intermediary between you and the Internet, the VPN service also hides your IP address. When you browse the Internet connected to a VPN server, the sites you visit see the IP address of the VPN server and not your real IP address. That way, you can keep your IP address private from prying eyes.

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What Are VPN Encryption Ciphers?

Encryption ciphers are cryptographic algorithms used to transform data into an unreadable format, ensuring the confidentiality and security of information transmitted through a VPN app. These ciphers play a crucial role in protecting your data from unauthorized access or interception.

Encryption Key Types

There are two types of encryption keys that can be used in encryption. These are the symmetric and the asymmetric encryption key. Symmetric encryption is a type of encryption where the same key is used for both the encryption and decryption of data. 

It’s a fast and efficient method of encryption widely used for securing data and ensuring its confidentiality. In this encryption type, the data is divided into fixed-length blocks, and the secret encryption key is applied to each block using a specific algorithm. The key is kept secret and must be shared securely between the sender and the intended recipient.

To encrypt the data, the key is used to transform the plaintext into ciphertext, which is an unreadable and scrambled version of the original data. The same key is then used to decrypt the ciphertext back into plaintext, effectively reversing the encryption process. In other words, you need the same substitution mapping to encrypt and decrypt.

Symmetric encryption is known for its speed and simplicity, making it suitable for encrypting large volumes of data quickly. However, it poses a challenge when it comes to securely sharing the secret key between parties, especially in scenarios where a secure key exchange is not feasible.

Unlike symmetric key encryption, asymmetric encryption uses two mathematically related keys, a public key and a private one. The public one is openly shared and can be accessed by anyone. It is used for encrypting data intended for the recipient. The private key is kept secret and known only to the intended recipient. It is used for decrypting the data encrypted with the corresponding public key.

The fundamental concept behind asymmetric encryption is that data encrypted with the recipient’s public key can only be decrypted with their corresponding private key. This allows for secure communication and confidentiality even when the public key is widely accessible.

Types of Symmetric Encryption Ciphers

Symmetric Encryption scheme

An illustration of symmetric key encryption from Wikipedia.

Advanced Encryption Standard (AES)

AES (Advanced Encryption Standard) is a widely used algorithm that provides strong security for data protection. It was established by the National Institute of Standards and Technology (NIST) in 2001 as a replacement for the aging Data Encryption Standard (DES). 

AES has since become the de facto standard for secure encryption in various applications, including VPNs. AES operates on fixed-size blocks of data, typically 128 bits, and supports key lengths of 128, 192, and 256 bits. 

The algorithm consists of several rounds of substitution, permutation, and mixing operations, performed on the input data using a symmetric key. These operations make AES highly resistant to attacks.

AES offers compatibility across different platforms, operating systems, and devices. The algorithm is a widely recognized and standardized encryption method, ensuring interoperability between VPN clients and servers. AES ciphers can be used in s like OpenVPN, L2TP/IPSec, and IKEv2/IPSec, among others. That said, it isn’t supported by the WireGuard protocol.


Blowfish is a symmetric key block cipher designed by Bruce Schneier in 1993. It’s known for its simplicity, speed, and strong security. Blowfish operates on fixed-size blocks of data (64 bits) and supports variable key lengths, making it a flexible algorithm for various applications, including VPNs.

One of the notable features of Blowfish is its key setup process. The algorithm uses a Feistel network, which involves dividing the encryption key into subkeys for each round. Blowfish can accept key lengths ranging from 32 to 448 bits, allowing users and VPN providers to choose the appropriate key size based on their security requirements.

Blowfish employs a series of substitution and permutation operations to encrypt and decrypt data. It operates on a 64-bit block of plaintext at a time and uses a series of iterations (rounds) to transform the data. Each round consists of a substitution step and a permutation step, which mix the data in a complex manner to ensure strong encryption.

Blowfish’s algorithm has been designed to be computationally efficient, allowing for fast encryption and decryption operations. This speed is particularly important for VPNs, where real-time encryption and decryption are necessary to maintain optimal connection speeds. Blowfish is a good fit for protocols like IKEv2/IPSec and OpenVPN.


ChaCha20 is a symmetric algorithm designed by Daniel J. Bernstein. It’s known for its simplicity, speed, and resistance to various cryptographic attacks. ChaCha20 operates as a stream cipher, generating a stream of pseudo-random bits combined with the plaintext using the XOR operation to produce the ciphertext.

One of the key advantages of ChaCha20 is its efficient implementation on a wide range of platforms, including both software and hardware. It is designed to be highly parallelizable, making it well-suited for modern processors and enabling fast encryption and decryption speeds.

ChaCha20 supports key sizes of 128, 192, or 256 bits, providing a strong level of security. It is also commonly used in conjunction with the Poly1305 message authentication code to ensure both confidentiality and data integrity.

Due to its speed, ChaCha20 has gained popularity and is widely used in various applications, including secure communication protocols like Transport Layer Security (TLS) and Internet Protocol Security (IPsec). 

Data Encryption Standard (DES)

The Data Encryption Standard (DES) is a symmetric encryption algorithm that was widely used in the past for securing sensitive data. It was developed in the 1970s by IBM and later adopted as a standard by the U.S. government.

DES operates on 64-bit blocks of data and uses a 56-bit key. The encryption process involves multiple rounds of substitution and permutation operations, known as the Feistel network. Each round applies a combination of substitution and transposition to the data, making it resistant to cryptographic attacks.

However, due to advances in processing power and the discovery of certain vulnerabilities, DES is now considered relatively weak and insecure against modern attacks. It has been largely replaced by more robust encryption algorithms, such as AES.

Types Of Asymmetric Encryption Methods

 Asymmetric Encryption scheme

Rivest-Shamir-Adleman (RSA)

Rivest-Shamir-Adleman (RSA) is a widely used asymmetric public key encryption algorithm named after its inventors Ron Rivest, Adi Shamir, and Leonard Adleman. It is known for its effectiveness in safe communication and digital signatures.

RSA utilizes the mathematical properties of large prime numbers and modular arithmetic. The algorithm generates a private-public key pair. The public key is shared openly, while the private key remains secret. The public key is used for encryption, while the private key is used for decryption.

To encrypt a message, the sender uses the recipient’s public key to transform the plaintext into ciphertext. Only the corresponding private key can decrypt the ciphertext back into the original message.

One of the key advantages of RSA is its resistance to factorization-based attacks. Breaking RSA encryption requires factoring extremely large numbers, which is computationally intensive and time-consuming. The security of RSA relies on the difficulty of factoring large numbers into their prime factors.

However, the strength of RSA depends on the key length used. A longer key length provides stronger security but requires more computational resources for encryption and decryption operations.

Elliptic Curve Cryptography (ECC) 

Elliptic Curve Cryptography (ECC) is a form of cryptography based on the mathematics of elliptic curves over finite fields. It provides a secure and efficient way to perform cryptographic operations, such as key exchange, digital signatures, and encryption.

In ECC, the basic idea is to use points on an elliptic curve as the foundation for cryptographic operations. An elliptic curve is a mathematical curve defined by an equation of the form y^2 = x^3 + ax + b, where a and b are constants. The curve also has a special point called the “point at infinity,” denoted as O.

The points on the curve form a group under an operation called point addition. The key strength of ECC lies in the difficulty of the elliptic curve discrete logarithm problem, which forms the basis of its security.

ECC offers several advantages over other cryptosystems, such as RSA. It provides the same level of security with shorter key lengths, resulting in faster computations and lower resource usage. This makes ECC particularly suitable for resource-constrained environments like mobile devices and embedded systems.

Diffie-Hellman (DH)

Diffie-Hellman (DH) is a key exchange protocol that allows two parties to securely establish a shared secret key over an insecure communication channel. It was invented by Whitfield Diffie and Martin Hellman in 1976 and is widely used in various cryptographic systems.

The basic idea behind the Diffie-Hellman protocol is the concept of a mathematical problem called the discrete logarithm problem. In simple terms, the discrete logarithm problem involves determining the exponent to which a given number must be raised to obtain another specified number, within a specific mathematical group. The security of the Diffie-Hellman protocol relies on the difficulty of computing discrete logarithms. 

How To Choose The Right Encryption Cipher

Choosing the right encryption cipher is crucial for ensuring the security and effectiveness of your VPN. Here are some key factors to consider when making your decision:

  • Security Strength — Look for encryption ciphers known for their high-security levels.  AES, with a key length of 256 bits, is widely regarded as one of the most secure options available today and is the standard in most VPN clients.
  • Performance Impact — Consider the impact of encryption on your Internet speed and overall VPN performance. Some encryption ciphers may be more computationally intensive, resulting in slower speeds. Strike a balance between security and performance based on your needs.
  • Compatibility — Ensure that the cipher you choose is compatible with your VPN client and the devices you plan to use. Check if the cipher is supported by your VPN provider and works well with your operating system or device.
  • Encryption Protocol — Consider the encryption protocols offered by the VPN service. Different protocols may support specific encryption ciphers, and they may have varying levels of security and compatibility. Choose a VPN that offers robust encryption protocols in addition to the cipher.
  • Trustworthiness — Evaluate the reputation and trustworthiness of the encryption cipher. Stick to widely recognized and vetted encryption ciphers to minimize the risk of vulnerabilities or weaknesses.
  • Future-Proofing — Consider the longevity and future relevance of the encryption cipher. Aim for ciphers that have undergone extensive testing, have widespread adoption, and are expected to remain secure for the foreseeable future.

How To Check If Your VPN Connection Is Encrypted

If you’re not sure whether or not your VPN encryption is actually working, there are a few free online tools you can utilize to check. My personal favorite is Wireshark. It’s easy to use and available for both Windows and Mac devices. Here’s how to use Wireshark to check your VPN encryption:

  1. Go to the official Wireshark page to download the app.
WireShark download page
  1. Follow the installation process to set up Wireshark on your device.
WireShark setup
  1. Run the program and select the network you want to test.
WireShark main screen with network choices
  1. Inspect the data packets.
WireShark network monitoring results

Note, if your VPN connection is properly encrypted, you shouldn’t see anything except unreadable sequences of encrypted data in the form of scrambled symbols, letters, and numbers.

Commonly Used VPN Protocols

Depending on the Virtual Private Network server you use, you will find different VPN protocols in the app. That said, most Virtual Private Networks feature a handful of the same security protocols. Here are the most common VPN protocols you will find with most VPN services:

  • OpenVPN — Open-source and widely used VPN software solution known for its robust security, flexibility, and support for various encryption algorithms. It offers strong encryption and is compatible with multiple platforms.
  • PPTP — An older protocol known for its simplicity and ease of setup. However, it has known security vulnerabilities and is not recommended for secure communications due to weaker encryption.
  • WireGuard — A modern and lightweight VPN protocol known for its simplicity and high performance. It offers secure encryption, faster connections, and efficient use of system resources.
  • L2TP/IPsec — A protocol combination that provides tunneling (L2TP) and encryption (IPsec). It offers good compatibility but has slower speeds compared to other protocols and is susceptible to certain attacks.
  • IKEv2/IPSec — A protocol that offers strong security and stability. Internet Key Exchange (IKEv2) IPSec supports seamless switching between network connections and provides reliable encryption for mobile devices.
  • SSTP — The Secure Socket Tunneling Protocol is a proprietary VPN protocol developed by Microsoft that uses SSL/TLS for encryption. It is primarily used on Windows operating systems and is the core security system in HTTPS.

WireGuard and OpenVPN protocols are the standards among most VPN companies. They generally offer the best-balanced performance suitable for casual VPN users.

How VPNs Encrypt Your Traffic

The process of encrypting your traffic begins with a VPN handshake, in which the VPN server and the VPN client start communicating after you connect to your chosen VPN server. Then, an asymmetric key exchange happens as a private and public key gets made.

After that, a symmetric key exchange occurs. A new and ephemeral key is created for every session. This is called perfect forward secrecy. This feature protects previous sessions in case of any future compromises.

The encryption algorithm uses a key like AES-256-GCM to encrypt your data. Then, algorithms check if anyone interfered with the encrypted connection during transit by using a mathematical hash function to scramble part of the data.

This is how a VPN encrypts your connection when sending data through the VPN tunnel. It’s an almost instantaneous process that happens after you connect to a VPN server. When the information from the VPN server reaches your VPN client, it uses its own private key to decrypt the message.

Why Do Most VPNs Use AES Encryption?

Most VPN providers prefer to use AES-256 encryption due to its recognized security and efficiency. One of the primary reasons for the widespread adoption of AES-256 is its security. The algorithm has undergone extensive analysis by cryptographers worldwide, and it has demonstrated resilience against known attacks. 

The U.S. government, for instance, has adopted AES-256 as the encryption standard for safeguarding classified information. The proven security of AES-256 gives VPN providers confidence in the protection it offers to users’ data.

Additionally, AES-256 is computationally efficient, especially when implemented using hardware acceleration or specialized instructions available in modern processors. This efficiency ensures VPN servers can offer high-speed encrypted connections without significant performance degradation. Users can enjoy a secure VPN experience without sacrificing connection speeds.

AES-256 is a standardized encryption algorithm that enjoys broad support across platforms, operating systems, and devices. This compatibility ensures that VPN services using AES can be readily deployed and accessed by users regardless of their preferred devices or operating systems. It facilitates interoperability and enhances the ease of use for VPN customers.

Lastly, by employing AES-256, VPNs can comply with these requirements, ensuring their services meet the necessary security standards. This is particularly important for VPN users who may have legal or regulatory obligations regarding data protection.

VPN Encryption FAQs

Is all data that goes through my VPN server encrypted?

No, not all data that goes through your Virtual Private Network server is necessarily encrypted. The encryption typically applies only to the data transmitted between your device and the VPN server itself.

Does every VPN client use encryption?

While the vast majority of reputable VPNs use encryption to secure your traffic, it’s important to note that not all VPN services might be doing so. Some VPN clients may employ weaker or outdated encryption protocols, potentially compromising your security.

How does VPN encryption work to secure Internet traffic?

VPN encryption works by creating a secure VPN tunnel between your device and the VPN server. When you connect to a VPN, your data is encrypted before it leaves your device using strong encryption algorithms. 

What is the best VPN encryption?

The Advanced Encryption Standard (AES) 256 is widely regarded as the best encryption available in the VPN industry. This algorithm has been extensively tested by cryptographic experts. AES 256 offers a high level of security against any brute-force attack.

What VPN encryption does NordVPN use?

NordVPN uses AES-256-GCM to ensure the security of its users’ data. Its OpenVPN protocol uses the 4096-bit DH key, while its IKEv2/IPSec uses 3072-bit DH keys. 

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