What is 256-bit Encryption? How Safe is It?
What is 256-bit encryption? It's something that every Certificate Authority and Reseller crows about when advertising their SSL certificates. And why wouldn't they? After all, encryption is what matters the most in an SSL certificate. But many users, including some of our parent company's customers, are unaware of the beauty that is 256-bit encryption.
So, let us break it down for you. Let's untangle the technology that is 256-bit encryption and understand how it secures everyone on the internet.
First, let's understand SSL Encryption.
It's a general perception that SSL Encryption is done using a key pair known as Public/Private Key Pair. It's also believed that Public Key Encrypts the data and Private Key decrypts it. In technical terms, this is called 'Asymmetric Encryption.'
However, there is a twist.
The actual encryption of data is not done through this Asymmetric method; it's done through Symmetric Encryption. Now the next question in your mind must be: "Then why is Public/Private Key pair used?" Well, it's used, but only for authentication. When client and server first come across each other, they need to verify each other's identity. That's where Asymmetric Encryption plays its part. This verification is done through the Public/Private Key Pair. Once the authentication is done and TLS handshake is performed, the actual encryption starts, and it's done through Symmetric Encryption. (If you're confused about Symmetric Encryption and Asymmetric Encryption, here's an excellent post for you.)
What is 256-bit encryption?
At first, the term '256-bit' sounds like nerd language. Well, it isn't. 256-bit encryption refers to the key length of the symmetric encryption technology. It means that the key is made of 256 binaries (zeroes and ones) and there are 2256 possible combinations.
Didn't get it? Okay, let's understand this with a simple example. Let's say there's a 2-bit key. Therefore, it will have 22 (4) values – 00, 01, 10 & 11. Thus, a 256-bit key can have 2256 possible combinations. Got it?
How Secure is 256-bit encryption?
"How Secure is 256-bit encryption?" "Is 256-bit encryption enough?" These are two of the most frequently asked questions when it comes to encryption level. Let us clarify once and for all: it's more than enough. There's a very solid reason behind our radiating confidence, and that's called 'Mathematics.'
The best way to crack an encryption key and that is 'brute-forcing,' trial & error in simple terms. So, if the key length is 256-bit, there would be 2256 possible combinations, and a hacker must try most of 2255 possible combinations before arriving at the conclusion (Typically, it takes around 50% keys to get the right combination).
On paper, 2256 may seem like a normal number, but don't you dare underestimate its power. 256-bit will have 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936 (78 digits) possible combinations. No Super Computer on the face of this earth can crack this.
Even if you use Tianhe-2 (MilkyWay-2), the fastest supercomputer in the world, it will take millions of years to crack the 256-bit encryption.