The Story

Imagine you have a secret message you want to send to your friend. You decide to put it in a special box with a lock that only your friend has the key to. But you also want to make sure that no one tampers with the box while it's on its way. To do this, you sign the box with a special seal that proves it came from you. This Go code does something similar, but with digital messages and encryption.

What the Code Does (ELI5)

1. Making Keys: The code first generates a pair of keys. Think of these like a lock (public key) and a key (private key). The lock is used to encrypt the message (put it in the box), and the key is used to decrypt it (open the box).

2. Encrypting the Message: The code takes your secret message and uses the lock (public key) and a special technique called OAEP to scramble it up. This scrambled message (ciphertext) is what you send to your friend.

3. Decrypting the Message: Your friend, who has the key (private key), uses it to unlock and unscramble the ciphertext. This turns it back into the original message.

4. Signing the Message: Before sending the message, you create a special code (signature) using the message itself and your private key. This signature is like your seal on the box, proving it's really from you.

5. Verifying the Signature: Your friend uses your public key to check the signature. If it matches the message, they know it hasn't been changed and it's really from you.

Why Each Step is Important:

• Keys: These ensure only the intended recipient can read the message (confidentiality).
• Encryption: This scrambles the message to keep it secret (confidentiality).
• Decryption: This unscrambles the message to make it readable (confidentiality).
• Signing: This proves the message is authentic (integrity and authenticity).
• Verification: This checks the authenticity of the message (integrity and authenticity).

How to Write It (Thought Process):

1. Import Tools: Include the necessary libraries for cryptography and formatting.
2. Generate Keys: Create a pair of RSA keys (public and private).
3. Encrypt: Use OAEP padding with the public key to encrypt the message.
4. Decrypt: Use OAEP padding with the private key to decrypt the message.
5. Sign: Create a PSS signature using the private key and the message's hash.
6. Verify: Use the public key and PSS to verify the signature against the message's hash.

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This code is about using encryption and digital signatures to keep messages secret and verify who sent them. Here's a step-by-step breakdown:

1. First, we import the necessary packages for cryptography and other functions we'll need.

2. In the main function, we declare variables we'll use later.

3. We generate a pair of keys: a private key and a public key. Think of these like a special lock and key pair.

4. We create a secret message we want to protect.

5. We use the public key to encrypt (scramble) our message. This is like putting our message in a box that only the private key can open.

6. We print out the encrypted message, which looks like gibberish to anyone who doesn't have the private key.

7. We then use the private key to decrypt (unscramble) the message, turning it back into something readable.

8. We print out the decrypted message to show it worked.

9. Next, we create a digital signature for our message. This is like a special stamp that proves we wrote the message.

10. We print out this signature.

11. Finally, we verify the signature using the public key. This checks if the message really came from us and wasn't changed.

12. If everything works, we print "Signature verified".

The thought process for writing this code might go like this:

1. "I need to keep a message secret. How do I do that? Oh, I can use RSA encryption."
2. "I'll need to generate keys for this. Let's start by importing the necessary packages."
3. "Now, I'll generate the key pair and create my secret message."
4. "Let's encrypt the message and then decrypt it to make sure it works."
5. "It would also be good to prove this message came from me. I can use a digital signature for that."
6. "I'll create the signature and then verify it to show how it works."
7. "At each step, I should print out the results and handle any errors that might occur."

This code demonstrates basic encryption and digital signature concepts, which are fundamental to many security systems.