Start here: secret codes

Six short lessons for young beginners, about five minutes each, with something to try. No math needed beyond counting. When you finish, the Book takes you further.

	Lesson	You will
1	Why keep secrets?	see the two jobs of cryptography: hiding and checking
2	The Caesar shift	make a code wheel and send a secret message
3	Cracking Caesar	break a code by counting letters
4	A code nobody can break	use dice to make a perfect secret, and see why it is hard to use
5	Locks and keys	send a secret to someone you have never met
6	Strong passwords	roll dice to make a password that is easy to remember and hard to guess

For teachers: each lesson works on paper, with a pencil, a few dice and a partner.