What Is PFS (Perfect Forward Secrecy)?

What is PFS?

VPN encryption is usually near impossible to crack, but it never hurts to go the extra mile and further secure your data and traffic. That’s where PFS comes into play.

What is PFS, you ask? We’re getting to that just now. What’s more, we will also discuss everything else you need to know about PFS as well - how it works, how VPNs handle PFS, and why it’s so important.

What Is PFS?

PFS stands for Perfect Forward Secrecy, and it’s also known simply as Forward Secrecy (FS). It’s an encryption style that revolves around a temporary Private Key (the key used to decrypt encrypted data) being produced in VPN client and VPN server communications for each session.

How Does PFS Work?

Basically, PFS encryption works by generating a unique session key for every single communication session initiated by a user between a client and a server. If, for any reason, a session key is compromised, the data from any other communication sessions will be safe. Once the generated Private Key is used up, it disappears, so it can no longer be compromised.

Furthermore, PFS encryption keys can even be refreshed within a single communication session, further limiting the amount of data that can be stolen by a cybercriminal if the temporary Private Key is compromised.

Compared to Perfect Forward Secrecy, regular encryption usually just has the client using the same Private Key for all client-server sessions. Essentially, that means there is a “Master Key” that can be used to decrypt all the traffic. If that key is compromised, all the data found in all communication sessions between the client and the server will be compromised as well.

With Perfect Forward Secrecy, there is no such “Master Key.”

Generally, PFS encryption can use the following key agreement protocols:

  • DHE-RSA
  • DHE-DSA
  • ECDHE-RSA
  • ECDHE-ECDSA
  • ECDH

What Is PFS in VPN Technology?

What about PFS in VPN client-server communications? How does that work?

Well, it pretty much works just like regular PFS encryption does. The main thing worth mentioning, though, is that both the VPN client and the VPN server must have PFS-enabled interfaces. Otherwise, Perfect Forward Secrecy won’t work.

Also, at a VPN level, PFS occurs during the “handshake” stage (when the server and client are authenticated and exchange keys) and the tunneling process (basically, the VPN connection).

Besides that, it should also be noted that PFS is normally used with certain specific VPN protocols, such as:

Keep in mind that PFS isn’t usually enabled by default. So, if you’re looking for a Perfect Forward Secrecy VPN, it’s best to choose a provider that makes it clear their service uses PFS encryption by default on certain protocols.

How Important Is Perfect Forward Secrecy?

PFS security is fairly valuable since it adds an extra layer of protection, ensuring your personal data is even safer on the Internet. That’s not to say regular encryption can’t protect your data well (provided strong ciphers and VPN protocols are used), but it never hurts to take extra security measures.

Encryption Algorithms

Plus, consider this – having a single Private Key act as a “Master Key” to all your online traffic is something that can actually be exploited. And that’s not a speculation since the NSA has used that weakness to gather valuable data before.

Besides that, there’s also the Heartbleed vulnerability that needs to be considered. It was essentially a bug found in OpenSSL (an open-source implementation of SSL and TLS protocols) back in 2012, which can potentially cause a leak of data of up to 64 kilobytes. Well, Perfect Forward Secrecy is the best way to protect your data from Heartbleed.

Considering all that, it’s clear that PFS ensures you get to enjoy a much more secure VPN connection. What’s more, PFS encryption is also likely to make cybercriminals much less likely to target the VPN server or client simply because all the effort that’s required to do so won’t be worth it since they’ll just get access very limited information.

Are There Any Drawbacks to Using PFS in VPN Technology?

Well, it is worth mentioning that Perfect Forward Secrecy might require more processing power, meaning it could take a little longer for the VPN connection to be established. Of course, that’s not guaranteed to happen all the time, and if your device has more than enough processing power, you might not even notice the delay.

Still, compared to the highly secure advantages of using a PFS VPN, it’s pretty obvious that a potential delay in the VPN connection process isn’t that bad of a trade-off.

Need a PFS VPN for Safer, Better Online Browsing?

Your security and privacy always come first for us, which is why we use Perfect Forward Secrecy by default on our OpenVPN and SoftEther VPN protocols (which are extremely secure encryption protocols, by the way).

What’s more, we also adhere to a strict no-log policy, meaning you don’t need to worry about us keeping tabs on what you do on the Internet.

Enjoy High-End Encryption as Well

The PFS security and extra-safe VPN protocols we offer go very well alongside our top-of-the-line VPN encryption. For starters, we use very secure ciphers like AES-128 and AES-256, plus RSA-2048 handshake encryption.

Besides that, we should also mention that our service uses the ECDH key exchange protocol, and reliable authentication encryption (SHA-256, SHA-384, and SHA-512).

Feel free to read our FAQ section if you’d like to learn more about what encryption CactusVPN can offer you.

Test-Drive Our Service for Free

Want to make sure our service can meet all your needs before making a commitment? No problem – you can try out CactusVPN free of charge for 24 hours before choosing a subscription plan.

And even after you choose one, you’ll still be covered by our 30-day money-back guarantee if something goes wrong.

The Bottom Line

So, what is PFS? Well, to put it as simply a possible, it’s an encryption feature that ensures a new unique Private Key (decryption key) is generated for every single VPN client-VPN server session initiated by you, as opposed to normally having a single Private Key for all your sessions.

This way, your personal data and online traffic are better secured since there is no way a cybercriminal would be able to access all your data if they would somehow manage to compromise a Private Key. With PFS, they would only be able to decrypt a tiny bit of information as opposed to the whole traffic, and said info would normally be useless to them.

Most VPN providers offer PFS encryption, but it’s best to choose a provider that makes it clear they use PFS by default on their VPN protocols.

Want to use a VPN provider that supports PFS?

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Tim has been writing content and copy for a living for over 4 years, and has been covering VPN, Internet privacy, and cybersecurity topics for more than 2 years. He enjoys staying up-to-date with the latest in Internet privacy news, and helping people find new ways to secure their online rights.