# File lib/httpclient/auth.rb, line 438
    def challenge(uri, param_str)
      return false unless NTLMEnabled
      if param_str.nil? or @challenge[uri].nil?
        c = @challenge[uri] = {}
        c[:state] = :init
        c[:authphrase] = ""
      else
        c = @challenge[uri]
        c[:state] = :response
        c[:authphrase] = param_str
      end
      true
    end