Asymmetric Encryption

The Key Exchange Problem
In Symmetric Encryption, Bob and Jane must share a secret key before they can communicate securely. But what if they live on opposite sides of the world? If they send the key over the internet, a spy might intercept it and read all their future messages!

Enter Public Key Cryptography

Asymmetric Encryption (also known as Public Key Cryptography) solves this by using a Key Pair. Instead of one shared secret key, we use two mathematically related keys, a Public Key and a Private Key. They are generated together using a mathematical formula, and they have a unique relationship: what one key scrambles, only the other key can unscramble.

• The Public Key This key is completely public. You can publish it on the internet or email it to anyone. It is used exclusively to scramble (encrypt) messages. Bob's Public is represented as a Triangle.
• The Private Key: This key is known only to the owner. It is used to decrypt messages. It is never shared or transmitted over the internet. Bob's private key is represented as a Star.

How Bob and Jane Share Secrets Safely

• Step 1: The Setup. Bob generates his key pair. Public Key and Private Key
• Step 2: Sharing the Public Key. Bob mails his Public Key to Jane over the open internet. The koala spy might see the Public Key, but it doesn't matter! Public keys are public information.
• Step 3: Sending the Secret. Jane then encrypts her top-secret recipe with Bob's Public Key.
• Step 4: Secure Delivery. Jane sends the Encrypted Message back to Bob. The spy intercepts it, but they don't have the Private Key, so all they see is a plain triangle. The recipe is safe.
• Step 5: Decryption. Bob receives the Encrypted Message. Using his hidden Private Key, he decrypts the message and reads Jane's recipe!