In 2003, Yang, Chang, and Hwang proposed an enhanced scheme of Peyravivan-Zunic’s password authentication scheme by using the Diffie-Hellman scheme. Later, Yoon, Ryu, and Yoo de...
Recently, Yang et al. improved Yang and Shieh's two password authentication schemes to withstand Sun and Yeh's forgery attacks. However, Kim et al. pointed out that Yang...