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copied!<p>You could use OpenSSL::Cypher</p> <pre><code># for more info, see http://ruby-doc.org/stdlib-1.9.3/libdoc/openssl/rdoc/OpenSSL/Cipher.html require 'openssl' require 'digest/sha1' # create the cipher for encrypting cipher = OpenSSL::Cipher::Cipher.new("aes-256-cbc") cipher.encrypt # you will need to store these for later, in order to decrypt your data key = Digest::SHA1.hexdigest("yourpass") iv = cipher.random_iv # load them into the cipher cipher.key = key cipher.iv = iv # encrypt the message encrypted = cipher.update('This is a secure message, meet at the clock-tower at dawn.') encrypted << cipher.final puts "encrypted: #{encrypted}\n" # now we create a sipher for decrypting cipher = OpenSSL::Cipher::Cipher.new("aes-256-cbc") cipher.decrypt cipher.key = key cipher.iv = iv # and decrypt it decrypted = cipher.update(encrypted) decrypted << cipher.final puts "decrypted: #{decrypted}\n" </code></pre> <p>But the intermediate form doesn't lend itself well to printing</p> <hr> <p>Given your thought that it would be nice if the intermediate form was the same length, you might just use a simple map of one char to another.</p> <h1><strong>PLEASE UNDERSTAND THAT THIS IS NOT SECURE</strong></h1> <p>You can <em>easily</em> brute force the key, but it seems to be congruent with your requirements.</p> <pre><code>class Cipher def initialize(shuffled) normal = ('a'..'z').to_a + ('A'..'Z').to_a + ('0'..'9').to_a + [' '] @map = normal.zip(shuffled).inject(:encrypt => {} , :decrypt => {}) do |hash,(a,b)| hash[:encrypt][a] = b hash[:decrypt][b] = a hash end end def encrypt(str) str.split(//).map { |char| @map[:encrypt][char] }.join end def decrypt(str) str.split(//).map { |char| @map[:decrypt][char] }.join end end # pass the shuffled version to the cipher cipher = Cipher.new ["K", "D", "w", "X", "H", "3", "e", "1", "S", "B", "g", "a", "y", "v", "I", "6", "u", "W", "C", "0", "9", "b", "z", "T", "A", "q", "U", "4", "O", "o", "E", "N", "r", "n", "m", "d", "k", "x", "P", "t", "R", "s", "J", "L", "f", "h", "Z", "j", "Y", "5", "7", "l", "p", "c", "2", "8", "M", "V", "G", "i", " ", "Q", "F"] msg = "howdy pardner" crypted = cipher.encrypt msg crypted # => "1IzXAF6KWXvHW" decrypted = cipher.decrypt crypted decrypted # => "howdy pardner" </code></pre>

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