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How does Encryption Work? (and Why it’s So Important)

Tuomas Rantalainen

01.09.16 4 min. read

We recently invited people to ask us anything they wanted about privacy on our Twitter channel. We answered some of them on YouTube, but so many questions touched upon encryption that we decided to give its own spotlight article.

If you’ve followed international news on business, tech or even politics lately, you’re likely to have seen the word “encryption” pop up all over the place. But while it’s often mentioned in the context of billion-dollar tech companies and superstar whistleblowers, it’s easy to forget that easy access to encryption greatly benefits even normal web users like you and me.


The History of Encryption

To understand encryption today, we must first look into the past. From around 1500 B.C. all the way to 40 years ago, encrypting text followed pretty much the same routine. People who wanted to pass encrypted messages to one another had to use something called symmetric encryption. This meant that there was one secret code (key), which would both to turn readable messages (plaintext) into an unreadable mess (ciphertext) and back to readable form.

This had two main problems: Firstly, all the communicating parties had to share copies of the secret key with each other. This meant either meeting to physically share the key or using a trusted courier. Secondly, keeping this communication private relied on all parties keeping the key to themselves.  If multiple people used the same key, everyone’s communication would be vulnerable if just one person was careless or compromised.

Public-Key Encryption

When  asymmetric encryption (more commonly known as public-key encryption) was invented and made public in 1976, it was a bigger deal than anyone could imagine. This system uses two keys instead of one. First there is the public key, the only purpose of which is to let the sender to encrypt plaintext into ciphertext. After the message has been encrypted, nobody (not even the sender) can open the message except for the person with the private key.

A simple way to understand this is to think of a post box with two keys to it. The public key lets you put letters in the box, but not look inside. The owner of the private key is the only one who has access to the contents of the box. The two keys are mathematically linked, but it’s not possible to use the readily available public key to get the private key. I know it sounds like magic, but it’s actually just an application of modular arithmetic.

Hard to Understand, Easy to Use

Now we know how encryption works, but what’s in it for the average person? You, like a lot of people, might be thinking “I have nothing to hide online, so why should I go through all the trouble of encrypting what I do?” First of all, there really is no hassle. The process of sending and receiving encrypted messages requires insanely complex equations, but machines do it for you. For instance, messages sent via services such as Whatsapp are automatically end-to-end encrypted so that nobody else except the people involved in the chat can see them, not even the service providers themselves.

A VPN app like our own Freedome also encrypts ALL your traffic automatically, protecting your information while hiding your tracks online.  As F-Secure researcher Christine Bejerasco puts it pretty brilliantly in the video below:

With VPN you become this online ninja, who is coming from somewhere and going somewhere else, but they don’t know exactly who you are or where you’re from”.

Why is Encryption So Important?

The average user should consider this: is your life really the open book you might think it is? If your web history, emails and instant messages contain no information you’d wouldn’t mind sharing with the world, then I applaud you. But the fact is, most of us do have secrets. Governments think they have the right to know them under the guise of security, criminals want to profit from them, and anyone who wishes you harm can intercept your online communications with increasing ease. Encryption doesn’t solve all of that, but it goes a long way towards keeping others out of your business.

The internet has given citizens of the world unprecedented power to communicate with each other, share ideas and together make this planet a better place to be on. Encryption lets us do this even in the face of censorship and repression, making its continued existence and legality all the more worth fighting for.

You might think that you have nothing to hide, but you have everything to protect”.
– Mikko Hyppönen, F-Secure CRO

Tuomas Rantalainen

01.09.16 4 min. read


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