patternShift.rb

hex = IO.binread("hex.txt").scan(/[0-9a-fA-Z]{2}/).map { |n| n.to_i(16) }
pattern = IO.binread("pattern.txt").split(",").map { |n| n.to_i }
IO.binwrite("output_added.txt",hex.length.times.map { |n| ((hex[n].ord + pattern[n % pattern.size]) % 256).chr }.join)
IO.binwrite("output_subbed.txt",hex.length.times.map { |n| ((hex[n].ord - pattern[n % pattern.size]) % 256).chr }.join