Comment on Xu et al.'s Key Agreement and Password Authentication Protocol

The Internet has been population, which it was implement information technology, to every enterprize, also changed their contact mode of information flow style. Since public key conception was proposed, it had authentication function to secure while they are communication, and defense the data to leak based on stranger. In 2010, Xu et al. proposed an improvement of generalized key agreement and password authentication protocol which it based on linear equation in two unknown of congruence. In this paper, we pointed out some errors. Thus, the Xu et al.'s improved scheme may not becomes to be correction