Comment on ‘Robust and efficient password authenticated key agreement with user anonymity for session initiation protocol-based communications’

The author comments on the paper by Zhang et al. (IET Commun., vol.8, no.1, p.83-91 (2014)). The Zhang et al. protocol for SIP authentication is robust against all known attacks, further it provide user anonymity. Zhang et al. have alternated the need of storing verification tables to reduce storage and computation burden on SIP server. The present author demonstrates a concern about the correctness of their protocol.