Perfect Forward Secrecy (PFS), also Forward Secrecy (FS), is an encryption system that regularly changes the keys used to encrypt and decrypt data
The concept of perfect forward secrecy has been around for a long time, but it is only recently that the term was coined.
The idea behind this security measure is to provide confidentiality guarantees on data even if the encryption key used to protect the data becomes known at some point in the future.
You can think of perfect forward secrecy as an insurance policy against future breaches and compromise of your encrypted information.
In this blog post, we will be discussing what perfect forward secrecy is and why it's important for your security. Perfect Forward Secrecy (PFS) is a property of some cryptographic protocols that require the key for each session to be unique.
How does perfect forward secrecy work?
Perfect forward secrecy is an encryption method that generates random public keys for each session, eliminating the key-storing vulnerability.
The “forward” part of the name comes from the way the keys are used to encrypt data that is flowing into the future at that moment. You can't go back and decrypt yesterday's messages because they were encrypted with a key that has been discarded.
In PFS, ephemeral keys are generated for each session and used in combination with symmetric encryption to protect the content. The public keys are then discarded after they've done their job, which leaves no trace of unencrypted data or plaintext keys on the system.
With the private key never leaving the system, there's no way to decrypt the content of past messages.
Is perfect forward secrecy important?
This question is frequently asked by those who are interested in security. Many don't understand why it should be considered necessary, while others believe it's an important part of public-key cryptography to rely upon.
So let's take a look at the basics of what it is, why it matters, and if there are any alternatives or substitutes to “perfect” forward secrecy.
Forward secrecy is a system that doesn't allow decryption of previously captured communication by using data obtained later. This can be achieved in two ways: In the first scenario, a temporary private key is generated for each session. This means that every session has a different set of keys, and it's impossible to decrypt past traffic without having complete access to the server at the time-zero.
A second approach is to use the ephemeral key exchange, which basically implies generating a new public/private key pair for each session.
This way, it's impossible to decrypt past communications even if the private key of the involved parties is compromised later.
Benefits of perfect forward secrecy
Forward secrecy is a cryptographic system that ensures the confidentiality of data in the future, even if the main secret keying material has been compromised. It will generate a unique new encryption key for each session; thus old decryption keys cannot be used to decrypt captured data transmitted through a specific connection. This feature can prevent attackers from capturing and abusing old encrypted data.
For example, the security of a system using perfect forward secrecy is not compromised when a laptop computer is lost or stolen; users' Internet traffic cannot be decrypted by anyone even if the private key for that user's certificate has been compromised (assuming no additional errors were made in the handling of that key).
The compromise of the server's private key material does not affect the forward secrecy of previously-generated traffic. This is like saying that once a piece of fine china has been broken, the fragments cannot be glued back together again.
This feature can provide additional security to sensitive data which needs to be protected even if the server's secret key(s) are compromised; for instance, if an attacker gains access to a database containing credit card information, only the information for those cards used by customers at that particular server can be decrypted. Session keys are then encrypted premaster secret keys with the internet engineering task force and key agreement phase.
A common use case is to protect user data on remote storage systems. Without forward secrecy, an attacker who can gain access to the remote storage system can compromise all data on it: past and future.
With forward secrecy, the compromise of secret-key material does not affect connections to that server made before the compromise occurred. It is difficult to generate a single session key with SSL protocol configuration and the same key exchange algorithm.
Similarly, if an attacker were to compromise the unique encryption key, unique session key, encryption keys, or private keys only that specific conversation would be leaked. They do not mandate the encryption cipher that must be used nor the means of actual key exchange.
If you are familiar with encryption, then you know that it is a process of converting data into something unreadable while keeping the original information intact. The goal of this process is to keep sensitive information safe from prying eyes and hackers while maintaining its integrity.
One aspect of security that people often overlook when using encryption is perfect forward secrecy (PFS). PFS ensures that an encrypted message cannot be broken by anything other than the key used to encrypt it in the first place. The session key generator is used with a symmetric cipher using the session key negotiated.
Perfect forward secrecy is a method of encrypting data so that the secret keys are not used more than once. If you only use your key to encrypt one message, then it's impossible for someone who intercepts the encrypted message to decrypt it with any other key.