shortwave numbers station style checkerboard numeric encoding + one time pad encryption http://users.telenet.be/d.rijmenants/en/table.htm http://users.telenet.be/d.rijmenants/en/onetimepad.htm see also https://linuxcoffee.com/numbers/ otp.py Usage: python otp.py filename encode|encypt|decrypt|decode test.bat Usage: test filename