This is how people are...at least in my experiences.

gistfile1.txt

key = [92, 28, 3, 18, 62-8, 49-2-10, 74-8, 922, 87-9, 102, 67, 17, 17.99, 105, 129, 147, 189, 202, 88]
msg = 'D6U17E2TPCZ6C8D2DND8C8C02335QF8OD1AS4A3947BDA3DB8VFAOG43B3ED8R69ER235L6BE72JLA9'.downcase
msg += 'DJGI948NXTPTEMWIOMGNNZTP'.downcase
msg += 'pe85$%99e0zfj'.upcase.downcase
msg += 'Q&,;k.4qD_L/fZ2P0zyP)??@~=$YL_uTk6<t>tr(%US4)v1>\jfk5zPrF|5\Rnf'
msg += 'LEm5n18AplaOGJxUS6F8vlF7SWgRuH23KlPObtlJaqeipkYYrtPVliafI8NfCJk'.chomp

decode = ''

key.map do |k|
  unless msg[k].nil?
    decode += msg[k-1] if (k.divmod(3).last == 0)
  end
end

puts decode.upcase!