Perfect Forward Secrecy: What It is, How It Works?

Ruheni Mathenge  - Streaming Expert
Last updated: May 22, 2023
Read time: 6 minutes Disclosure

Perfect forward secrecy is a great way to stay safe online. Check out this guide to know what it is, how it works, its pros and cons, everything.

Perfect Forward Secrecy (PFS) is a unique encryption protocol that provides robust security to online traffic. It ensures no data leak even if the cyber attacker steals the private encryption key to decrypt the information. PFS utilizes a key exchange algorithm that changes the session encryption key after every message, call, and web reload. This way, only a bit of your data can be compromised upon breach, and the major data will stay encrypted and protected. This article sheds light on Perfect Forward Secrecy and its operation to protect online activities.

Any data transmitted online remains vulnerable to unauthorized interception or even download. This can include personal or sensitive data like passwords, credit card numbers, and bank account details. So, finding an effective way to protect this information is essential.

In addition, a hacker may retrieve your past conversations upon getting hold of your private keys. Perfect forward secrecy (PFS) is one of the best ways to prevent this from happening and keep you safe online.

What is Perfect forward secrecy?

Perfect forward secrecy (PFS) is an encryption type that regularly changes the encryption key to protect your online activities. So, only a tiny bit of your data will be compromised in case of a security breach.

It is designed to switch keys after every call, message, and web page load. As a result, the intruder will only manage to get one message or operation because the rest of the data is encrypted with different keys.

The system will also safeguard the data of networks using the SSL/TLS protocols if their assigned keys are compromised.

How perfect forward secrecy works

Let us assume you are chatting with a friend through a secure messaging app that uses perfect forward secrecy. Also, the app has public and private keys that will encrypt your communication and identify the intended sender and receiver. These keys help your friend and you to recognize each other.

The key exchange algorithm will then create a temporary key to encrypt every single message. Therefore, when you send a message to your friend, the key will encrypt it. At the same time, your friend will decrypt the message with the same key. This process repeats with new session keys every time you send a message.

Therefore, even if a hacker manages to intercept your conversation, they will only access a single message and not the whole chat. Moreover, if they obtain your public and private keys, they can’t see your dialogue as every message is encrypted with different keys. Unfortunately, malicious actors can fake your friend or your identity and potentially snoop on future conversations.

Why is perfect forward secrecy hot right now?

A couple of major incidents happened in recent years that made perfect forward secrecy widespread in cyber security.

The first case is when Edward Snowden revealed how the US government collects network traffic secretly. So, if an institution can conduct mass surveillance, then anyone can. Snowden showed that secret surveillance is a reality rather than a possibility.

Even so, the IT community had been facing the risk of data compromise for years. Unfortunately, hiding a secret for long only gave malicious actors more time to figure out how to access it. Thankfully, the long-term SSL keys brought a sigh of relief by introducing advanced security to manage the risk.

The second critical incident was with the Heartbleed vulnerability that showed how OpenSSL could be attacked easily. After accommodating the long-term SSL keys for so long and from Snowden’s revelation, the IT community needed a more transient key exchange method.

In 2016, Apple decided that all apps in the App Store must employ perfect forward secrecy. Fast forward to 2018, the Internet Engineering Task Force (IETF) completed the new TLS 1.3 standard that orders PFS for all TLS sessions.

Unfortunately, the benefit of PFS is also its biggest downside. Hackers cannot decrypt your information unless they use one of two specific decryption approaches. Sadly, in the same way, your team cannot either.

What is perfect forward secrecy used for?

Perfect forward secrecy

Some of the uses of the perfect forward secrecy are: