Diffie Hellman

In communication, we need to have a symmetric key to communicate securely. If we share our secret keys it will not be secure. If someone gets the secret key then they can decrypt messages. Diffie Hellman algorithm is introduced to solve this issue.

The Diffie Hellman algorithm was published in 1976. It is so much regularly used algorithm in day to day communication. When you want to login to the browser to watch something you perform a Diffie Hellman key exchange. 

Now I'd like to explain Diffie Hellman in two different ways.

• The Color Representation Method
• The Mathematical Method

It is more suitable to begin in the color method because it will explain the DF algorithm nicely in a non-mathematical way.

• The Color Representation Method

In cryptography, we take two communication parties, Alice and Bob, as usual. We take private keys of Alice as red color, Bob as blue color and the public key of both of the parties as Yellow color.

Then Alice will take the public key Yellow and mix it with its private key Red. Then the result will be an orange color key.

Bob will take the public key Yellow and mix it with its private key Blue. Then the result will be a Green colored key.

Now Alice has an orange key and Bob will have Green key in addition to their public keys, and private keys.

Now they will share these keys in between them like Alice will share his orange key to Bob and Bob will share his Green key to Alice. 

After the color exchange happened then the Bob will have the Orange color key and Alice will have the Green Color key.

Then Alice will mix his secret key which is Red with Bob's color Orange and then he will derive the brown color. and also Bob will mix his secret key which is blue with Alice's color Orange and he will derive the brown color key.

 Now you can see there is common key which is available to both parties which is the color brown.

They can use this as a symmetric key to communicate securely.

This is a summary of DF algortithm as a whole diagram.

In here you can see that we have derived a symmetric key. In here Alice and Bob will only exchange their orange and green color keys to derive this key. If a somebody outside sees the color orange he cannot guess what colors were mixed to make color orange what color ratios are used.
So we can ensure that outside parties cannot guess the private keys of Alice and Bob.