In this note we've discussed just a few ideas related to
cryptography. There are many others, most of which use quite
sophisticated mathematics. The National Security Agency, which is the
U.S. government agency dealing with cryptography, is reportedly also
the largest employer of mathematicians in the world. (We don't really
know, because they keep this information secret!)
8 The Hill Cipher
V'ir Tbg n Frperg 
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