Bcrypt Encryption, Decrpytion copied from devise

gistfile1.rb

 # constant-time comparison algorithm to prevent timing attacks
 def secure_compare(a, b)
  return false if a.blank? || b.blank? || a.bytesize != b.bytesize
  l = a.unpack "C#{a.bytesize}"

  res = 0
  b.each_byte { |byte| res |= byte ^ l.shift }
  res == 0
 end
 
 
 # Verifies whether an password (ie from sign in) is the user password.
  def valid_password?(password)
    return false if encrypted_password.blank?
    bcrypt   = ::BCrypt::Password.new(encrypted_password)
    password = ::BCrypt::Engine.hash_secret("#{password}#{self.class.pepper}", bcrypt.salt)
    secure_compare(password, encrypted_password)
  end

  # Digests the password using bcrypt. Custom encryption should override
  # this method to apply their own algorithm.
  #
  # See https://github.com/plataformatec/devise-encryptable for examples
  # of other encryption engines.
  def password_digest(password)
    ::BCrypt::Password.create("#{password}#{klass.pepper}", :cost => klass.stretches).to_s
  end