Rainy-Day Rescue: Number-Grid Cipher

Reading Time: 2 minutes

We recently had a rainy weekend interrupt our original plans to go geocaching. Instead, I took inspiration from John Baichtel’s recent posting – Codes For Kids –  to introduce my kids to ciphers.   Specifically the Number-Grid (or Polybius Square) cipher.

The NSA’s CryptoKids website is a great place to help introduce your kids to codes and ciphers.  The flash-enabled site sports cartoon-characters and step-by-step instructions on how to encode (and decode) various codes and ciphers.  I chose the Number-Grid cipher as one that was appropriate to all my kids.

I started with some loose-leaf paper and a couple of crayons:


From there I wrote out a cipher for each of my kids and showed them how to start decoding the cipher:


My oldest son got the hang of it and wrote a note back to me:


The end result – an hour or so spent at the kitchen table having fun together when we should have been geocaching….if only the weather had cooperated.

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