Key agreement protocol is one of the most important cryptography protocols which are used to build a shared secret key between two or more participants through an insecure channel. To increase the security and efficiency of these protocols, many studies have been carried out. Recently, in 2012, Lee et al. proposed a key agreement protocol using smart cards and claimed that their protocol is secure and practical. However, the researcher proved that the researcher's protocol is vulnerable to the privileged insider attack and the denial of service attack, and also the protocol cannot protect the user's true identity.