How to Securely send Messages

Here, letterbox is the box that contains the letter not the letterbox of your home, where the postman puts the letter.

First you buy(make) a ton of locks that can be locked without a key but can't be unlocked without your key. There should only be one key that unlocks the lock and only you should have it. Then, you distribute your locks everywhere where your friends who send you important messages live, distribute them in public, they're just locks that only your key can open. maybe send a bag or two of those locks to them.

When sending you a letter ask your friend to quickly lock their letter in a box becomes letterbox with their own lock+key that both locks and unlocks the box for convenience. Then ask them to lock their key that they used to lock the letter box (letterbox-key) using the lock you have given, whenever they are sending you a letter. The message is secured.

Now tell them to parcel the letter That is locked using their key and their key is locked with your key in any way they want because no one except you can unlock that box since only you have the key to unlock the box to get their key that they used to lock the letter. You get two boxes, a box that contains the letter, and another box that contains the key of your friend to open the letterbox secured by your lock.

To open the letter you open the lock of the box that contains the letterbox-key using your key. Then you open the letterbox using the letterbox-key. then you throw the letterbox lock+key that your friend used because it's only needed once -- like a disposable lock. And enjoy the letter.

Your friend locked the letter with his own lock+key first because it is easier for them to lock the letter with their own key, and it's simpler to lock that small key with the lock you've given.

This is how PGP works. In summary:

1. You distribute your public "lock" to everyone.
2. Your friend uses a temporary lock (symmetric key) to secure their message in a box.
3. They then secure the key for that temporary lock by locking it with your public lock (asymmetric encryption).
4. Only you have the key (private key) to open that envelope and retrieve the temporary key, which then allows you to unlock the box and see the message.

And that's how we send encrypted emails.