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End to End Encrypted Communication Explained in Simple Terms

How does encrypted communication work?

Click to watch the video tutorial instead.
Encryption is like a lock. Ideally, only you should have the key to unlock it.
When you connect to a website (bank, online backup storage and social media) and transfer private data, it goes through various internet companies. You do not know how trustworthy these companies and their employees are. This is why you lock (encrypt) the data between you and the website, so anyone in between won't see it. Internet browsers automatically do this the website supports secure HTTPS.

There are two computers on front of you. The Green one is me and the The Red one is my bank. In between us we have the internet service provider (ISP).

I'm about to connect to my bank and send some sensitive information, like logon credentials or the account number. Instead of a bank, it could be a file backup storage like Google Drive, Microsoft OneDrive, DropBox, or a place where I keep my private photos, tax return papers, medical records etc.

When I send this information to them, I know that they can see this information, and I'm OK with that because I chose to use their service. Whenever the government wants to see someone's information, they contact the bank, Google or Microsoft and ask for that information. That's reasonable.
Before my information reaches the bank, it has to go through many computers and networks. First, it reaches the local router my computer is connected to.

It can be my home router or the one in Starbucks. Then it goes through my ISP (Internet Service Provider) like Verizon.

Then the message reaches my bank.

Since the message passes through so many companies, their networks and computers, I want to make sure these these companies and their employees are not capable of stealing my message. This is why my browser encrypts the message before sending it. In this tutorial I will refer to encryption as LOCK (to make it simple). Only I have the key to unlock my lock. So I encrypt my message with my lock. Let's name my lock ML.

The message is now locked (encrypted). I will go ahead and send the message now. It passes through my network (or Starbucks).

It then reaches the ISP. If the ISP tries to read the message, or, there is a hacker who managed to hack into ISP's network and intercepts my message, they will not see the content of my message because it's locked with ML

The same way, my router or Starbucks' router could get hacked instead of the ISP. It is relatively easier to do with public WiFi (Starbucks). The message continues to travel until it reaches my bank. The bank can't read the content because they don't have my key to unlock my lock.

So what does the bank do? They add their own lock. Let's call it BL (Bank Lock). Now the message is encrypted with two locks (ML and BL).

Then the bank sends the message back to me without reading it, because they could not. The ISP or their hackers still can't read it because it's encrypted.

I receive my own message. When I say I, I mean my browser, an encrypted app like Snapchat, backup software etc. Once I have the message, I remove my own lock from it. Now the message is only locked with the bank's lock.

I send it back to bank again. Hackers still can't read my message because it's still locked, but this time only with the bank's lock.

The bank finally receives my message, and since it's only locked with their own lock, they can unlock and read its content.

This was a basic explanation of how the encryption communication works. As you can see, it's important that only I have the key for my lock, and only the bank has the key for the bank's lock. Otherwise the sensitive information can be compromised and de-crypted. There has been a discussion on internet about laws that force companies to add backdoors into encryption. What that means in simple terms, is that the government wants to have the copy of the key that my bank and I use for communication. They will promise to keep those copies of locks safe. The Problem is, they cannot keep it safe because hackers can hack into government and steal the copies of our keys.

After that, if hackers intercept my message, they will be able to unlock and read its content. They will be able to do this for hundreds of millions of people who use the internet. That is what an encryption is supposed to prevent, so introducing backdoors and breaking encryption is a bad idea because it threatens the whole internet.