restful-authentication/lib/authentication/by_password.rb

by_password.rb

    module ModelClassMethods
      # This provides a modest increased defense against a dictionary attack if
      # your db were ever compromised, but will invalidate existing passwords.
      # See the README and the file config/initializers/site_keys.rb
      #   
      # It may not be obvious, but if you set REST_AUTH_SITE_KEY to nil and
      # REST_AUTH_DIGEST_STRETCHES to 1 you'll have backwards compatibility with
      # older versions of restful-authentication.
      def password_digest(password, salt)
        digest = REST_AUTH_SITE_KEY
        REST_AUTH_DIGEST_STRETCHES.times do
          digest = secure_digest(digest, salt, password, REST_AUTH_SITE_KEY)
        end 
        digest
      end    
    end