random_subst_cypher.rb

require 'pp'

input = <<eos
Hello there
eos

# Randomise order of a-z
rand_characters = ('a'..'z').sort_by { rand }

encoding = Hash.new
rand_characters.each_with_index do |letter, index|
    encoding[letter] = index + 1 # Let's make it 1..26
end

output = Array.new
# Arrays of arrays
input.downcase.split(/\s/).each do |word|
    # Swap from letters to numbers
    word_arr = word.split('').collect do |letter|
        encoding[letter]
    end

    output.push( word_arr )
end

pp output