1. Public Key Cryptography

2. Ken Coder
Ken Coder wants to send a message to his sister,

3. Dee Coder
Dee Coder. But they have a problem.

4. Yves Dropper
Yves Dropper reads all their mail!

5. Ken's idea
I will lock my message in a box.

6. Yves can't open it
Then Yves Dropper will not be able to open it.

7. Neither can Dee.
Unfortunately, neither can Dee.

8. Ken sends a secret key
No problem! says Ken. I will send Dee my secret key.

9. Yves reads all the mail!
But Yves reads all the mail, and copies the key.

10. Ken sends the box…
Then when Ken sends the box…

11. Yves can read the message.
But Yves can read the message too.

12. Dee's Idea
I have an idea, says Dee.

13. A box with 2 keys
I will make a box with two keys!

14. One key for locking the box…

15. and one key for unlocking the box!

16. Send everyone the locking key

17. Keep the unlocking key

18. Diffie & Hellman
Public Key
Cryptography

19. 2 Keys

20. One Encoding Key

21. One Decoding Key

22. Public Key Directory

23. Private Keys stay private

24. Anyone can send a secret message!