Blockchain cipher suitable for preschoolers Is there a cipher that well suited for preschool-aged children to work out on pencil and paper, to learn concepts of block chains?

It must have the following requirements:


Able to be easily verified
a. For example, Joe submitted red, but Suzy submitted blue. Everyone knows Suzy is right...somehow. (Color-specific results are not required but used to illustrate that the cipher need not be number-based, although that is fine too)
Able to be easily ciphered with pencil and paper, or drawings, or in a child's head
Able to use a previous result (minus the genesis of course), to create a 'blockchain' of sorts


The cipher may be low-complexity. It does not matter if it is easily broken.

Most ciphers are geared towards being easy to verify, but difficult to decipher. This situation is a bit different in that it does not have to be difficult to decipher. Out of the box ideas are quite welcome.
I'd suggest you don't try to create or use a cipher.  Rather, I think maybe a more interesting way to view blockchain systems is as a log that is created through a distributed lottery.

So, in lesson one, you could describe how to keep track of something (account balances?  something more relevant?) via a sequence of log entries written on the board.  This would be a centralized scheme.

In lesson two, you can make it distributed.  In each stage, have a lottery where you randomly pick one of the students to win the lottery.  The winner of the lottery gets to write down the next log entry on the board.  Everyone else watching can see whether that student did it correctly and fairly.  If not, the next winner ignores the bogus stuff written on the board.

No cryptography is needed.  You just need a way to randomly pick one student in the room, in a fair way.  This could be done with numbered balls in a box, or any number of other ways.