What is Perfect Forward Secrecy (PFS), and How it Works?

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Perfect Forward Secrecy (PFS) is a security feature built into many encryption algorithms. It ensures that even if someone steals your private key, they won’t be able to decrypt any past encrypted messages.

This article will learn about Perfect Forward Secrecy (or PFS). We will also see why encrypting our data with PFS is important.

We will also look at how PFS works and protects us from hackers.

What Is PFS?

Perfect forward secrecy (PFS), sometimes referred to as “forward secrecy,” is a cryptographic technique used to ensure that once a secret key is compromised, it cannot be re-used to decrypt previous messages sent over a network connection.

This ensures that even if one part of a communication system is compromised, the entire conversation can still be read.

The term “perfect” refers to the fact that the system’s security does not depend on anything else; there are no weaknesses in the design or implementation of the protocol.

Perfect forward secrecy (PFS) encrypts data such that even if one party loses control over their private keys, the data cannot be decrypted. This is achieved by generating a unique secret key for every communication session and keeping those secrets safe.

In practice, you must use different devices for every connection, making it harder for hackers to steal your credentials.

The problem is that both parties must agree upon a shared secret beforehand, which isn’t always possible.

For example, if you’re connecting via a public Wi-Fi hotspot, there’s no way to know whether the network operator will keep records of your activity.

If you connect to a VPN provider, however, they’ll usually provide you with some form of authentication, allowing you to establish a secure channel.

The Main Purpose of PFS

In April 2016, the Internet Engineering Task Force (IETF), a group of global experts working together to develop web standards, published RFC 7469. This document describes Perfect Forward Secrecy (PFS).

In short, it explains how to prevent attackers from recording encrypted data over extended periods of time.

This is done by generating a unique session key per SSL/TLS session. The server generates a different key when the session ends, which is then securely destroyed. This way, even if an attacker gets hold of the public key associated with the session, he cannot use it to decrypt previous communications.

As a side effect, PFS makes it harder for man-in-the-middle attacks to succeed. For instance, a compromised CA certificate authority can no longer issue valid certificates for TLS and HTTPS connections.

Most major browsers and operating systems now support Perfect Forward Secrecy.

How Does PFS Work?

Perfect forward secrecy (PFS) is one of the most important things you can do to protect your online privacy. This type of encryption keeps the contents of your communications secure even if someone hacks into your email account.

Once you use PFS, you won’t ever have to worry about losing your messages again because they’ll be safe forever.

PFS encryption works like this: basically, PFS encrypts each individual communication session between your computer and the web server.

When you start a connection, you generate a random session key specific to that particular session. Then, the session key is encrypted with your public key and sent over the Internet.

The session key is decrypted on the receiving end with your private key and then re-encrypted with the original session key.

This way, even if someone intercepts the session key during transit, they still cannot read what you are sending or receiving without breaking the encryption process.

The problem with regular SSL/TLS encryption is that it doesn’t work well with mobile devices. For example, if you try to connect to a website via your phone, the browser generates a new session key for every request.

However, it uses the same session key for all requests. So, if someone gets access to your session key, they could steal everything you’ve been doing on that device.

With PFS, however, the session key changes for every session. So, even if someone steals the session key, they still can’t see anything unless they hack into your computer.

Which Encryption Algorithms does PFS use it?

SSL/TLS is accomplished by exchanging keys via Agreed Cryptographic Processes Called Cipher Suites.

These connections are established through a process known as a Handshake. This handshaking process establishes the connection parameters, including the cipher suite(s), authentication method, and shared secret.

In addition, it also determines whether Perfect Forward Secrecy (PFS) is required. PFS ensures that the session key cannot be compromised even if the server is later breached.

Currently, two key exchange algorithms exist Ephemeral Diffie Hellman (DHE) and Ephemeral Elliptical Curve Diffie Hellman (ECDHE).

DHE is considered secure because it does not require additional security measures like certificates.

However, ECDHE is preferred due to its faster performance and greater compatibility. Both protocols support RSA and elliptic curve cryptography (ECC).

What Is PFS in VPN Technology?

Perfect Forward Secrecy (PFS) is one of those terms you hear thrown around a lot in network security but don’t understand what it is.

In short, PFS provides a way for a VPN client and a VPN server to communicate securely even if someone intercepts the data being sent over the Internet. So, why do we care about PFS in VPN technology? Let us explain.

The most common use case for a VPN involves connecting to a remote network via a public Wi-Fi hotspot.

If you connect to a secure VPN server, you gain access to your corporate network without worrying about eavesdroppers snooping on your traffic.

However, if you want to protect against man-in-the-middle attacks, you might consider connecting to a VPN server within your organization. This setup ensures that your connection to the VPN server cannot be intercepted by anyone else.

In addition to protecting against eavesdropping, there are some additional benefits to using PFS in VPN connections.

For example, suppose you use PFS to encrypt a connection between a VPN client and a remote server. In that case, the encrypted information will remain intact no matter how often the connection is broken down.

Therefore, if someone breaks into your system and steals your credentials, they still won’t be able to decrypt the information stored on the stolen device.

While PFS isn’t necessary for every VPN connection, it’s something to keep in mind.

And since it’s part of the OpenVPN protocol, we know it’ll be supported in future versions of the open-source software.

What are the benefits of using Perfect Forward Secrecy?

Perfect forward secrecy (PFS) is a cryptographic protocol to prevent key disclosure attacks against encrypted communications.

Suppose you’re familiar with public/private keys. In that case, you might know that one of the main purposes of using them is to ensure that the communication channel cannot be decrypted without knowing the corresponding secret key. This is what makes encrypted communications secure.

However, the problem arises when someone intercepts a communication and gets access to the information sent over the network. They could use the intercepted data to decrypt future messages.

To combat this issue, PFS uses different encryption keys for each session. So even though someone has managed to gain access to a previous session, they won’t be able to decrypt any further sessions.

In addition to preventing such attacks, PFS also provides another benefit: it allows you to revoke old keys and generate new ones whenever necessary.

Revoking older keys is often required to comply with regulations like PCI DSS, HIPAA, etc., where companies must keep records for longer periods of time.

This feature is especially important for organizations that store sensitive data online. For example, many banks require customers to input their banking credentials every time they log into their accounts; however, once those credentials expire, the bank loses track of them forever.

With PFS enabled, the bank can simply delete the expired credentials and regenerate new ones.

So why isn’t everyone doing this already? Well, it turns out that most people aren’t aware of this feature. Many assume they no longer need to worry about protecting their keys because they’ve been encrypting their data securely for years. But that’s not true.

Even if you’re encrypting your data properly today, you still need to ensure that the next person who handles your data doesn’t have access to your keys. Otherwise, they’ll be able to decrypt your data.

That’s why we recommend enabling PFS on your web servers. You can do this easily with NGINX, Apache, IIS, Nginx, HAProxy, and others.

What are the Disadvantages of Using PFS in VPN Technology?

If you’re looking to use a VPN service, you’ll want to ensure that it supports Perfect Forward Secrecy.

This feature ensures that no one can decrypt the data that you send over a VPN tunnel, even if they know what encryption algorithm you use.

Perfect Forward Secrecy requires more processing power than traditional VPN protocols like PPTP and L2TP/IPSec.

Some argue it takes too much CPU power to establish a perfect forward secrecy connection. However, there are ways around this problem.

For example, the OpenVPN protocol allows you to specify your computer’s computing power to establish a connection. This way, you don’t need to worry about whether your device has enough horsepower to support PFS.


Perfect Forward Secrecy is a powerful tool that can help keep your data safe.

By ensuring each session has its own key, PFS ensures that even if one session is compromised, the others remain secure.

PFS is an important part of keeping your data safe, and it’s something you should be aware of when choosing a security protocol.