Encryption simply explained using paints (not technical)

Full video explanation

How did people within a country transmit secure messages over radio that anyone can hear during war?

Picture the following situation. You are in a room full of people and you meet someone for the very first time. How do you tell him a secret without everyone else in the room eavesdropping and listening in on your secret. You both have met for the first time so you can cross out the possibility of having set up any prior code words etc. Welcome to the internet where everyday you visit web pages for the first time and still manage to connect to them securely. (This website is also securely connected. Just look at the address bar and you will see https: instead of a http. The ‘s’ in https means secure.)

Public key encryption allows us to solve the problem of sharing private information with strangers without prior contact/ agreements. The whole concept revolves around it being easier to mix things than unmix them.

Let me explain how this is possible using paint. (I will also label each paint color with a letter to make it easy to follow)

Using colored paints to understand encryption

Step 1: Both people pick a private color.

Encryption simply explained step 1
Step 1

Lets say person A picks private color Red and person B picks private color blue. At no point is this private color shared.

Step 2: One person declares a public color (Color C).

Encryption simply explained step 2
Step 2

At this point one of the person will release a color that is different from their private color. To share this color with the second person, the first person has to release in the public by saying it out loud.

Step 3: Secret + public color

Step 3

Both the people mix their secret color with their public shared color (person 1 gets color a*c, person 2 gets color b*c).

Step 4: Share color mixture publicly

Encryption simply explained step 4
Step 4

Then both parties will share the color mixture with the other person publicly. So far the public knows the original share color, and each person’s mixture of their private color with the public color.

Step 5: private color + other person’s mixture

Encryption simply explained step 5
Step 5

Each person takes the other person’s mixture and mixes it with their private number (person 1 gets color a*b*c, person 2 gets color a*b*c). At this point both the mixtures will be the same and this is a key they can use to lock any information they share publicly without anyone knowing what this is. 

Step 6: What does the public know

Encryption simply explained step 6
Step 6

The public cannot derive our key from the publicly shared information since they don’t know how to un-mix the colors. If they try to mix the colors that are publicly available, they will get the following combinations- (color A * B * C *C), or (A * C * C) or (B * C * C). They will have extra information that they can’t un-mix to find the original color

Encryption simply explained step 7 what information can the public guess
What information can the public guess

Modern encryption on the internet

In actual encryption, instead of paint, people use numbers. Take the number 64. It can be formed by multiplying 2*32 or 1* 64 or 4*16 or 8*8 (equal to mixing paint). Just knowing the mixed number– in this case 64– doesn’t tell us what numbers were used to create it, multiple methods of creating that number/paint color exist.

Do note that computer encryption uses much bigger numbers than the number 64 I demoed. Furthermore, they use more complex formulas than the simple multiplication formula I used.(person 1 gets color a*c, person 2 gets color b*c)

Further reading sources:

Link 1: https://medium.com/@vrypan/explaining-public-key-cryptography-to-non-geeks-f0994b3c2d5

Link 2: https://en.wikipedia.org/wiki/Public-key_cryptography


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