ELI5: Explain Like I'm 5

Kagema

Okay, so imagine that you have a secret that you don't want anyone else to know. Maybe it's a surprise party you're planning for someone, or maybe it's just something embarrassing that you don't want anyone to find out.

Now imagine that you live in a time when people didn't have phones or email or even texts. The only way to communicate with people was in person or with a letter.

But sending a letter can be risky. What if someone intercepts it and reads your secret? That's where kagema comes in.

Kagema is a special kind of Japanese letter writing that was used in the past to keep secrets from prying eyes. When someone wanted to send a private letter, they would use kagema to encode the message.

To do this, they would write the message using special characters that were only known to them and the person the letter was meant for. These characters could be numbers or symbols or even made-up words.

For example, instead of writing "I am planning a surprise party for you," they might write "39167259 28394228 30231022 03310586 48583246." Unless you knew the code, you wouldn't be able to understand the message.

Kagema was a very clever way to keep secrets, but it also required a lot of trust. You had to trust that the person you were sending the letter to would be able to decode the message correctly.

Today, we have much more secure ways of communicating, but kagema is still an interesting part of history that shows how people used to protect their secrets.