RESUMO
Three-party authentication key exchange (3PAKE) is a protocol that allows two users to set up a common session key with the help of a trusted remote server, which is effective for secret communication between clients in a large-scale network environment. Since chaotic maps have superior characteristics, researchers have recently presented some of the studies that apply it to authentication key exchange and cryptography. Providing user anonymity in the authentication key exchange is one of the important security requirements to protect users' personal secrets. We analyse Lu et al.'s scheme which attempts to provide user anonymity and we prove that his scheme has errors in the key exchange phase and password change phase. We propose a round-effective three-party authentication key exchange (3PAKE) protocol that provides user anonymity and we analyse its security properties based on BAN logic and AVISPA tool.