An Improved User Authentication Scheme for Hierarchical Wireless Sensor Networks without Tamper-Proof Smart Card

Recently, Maitra et al. proposed an efficient and robust user authentication scheme for hierarchical wireless sensor networks. They claimed that their scheme does not need tamper-proof smart card and resisted different possible attacks include smart card stolen attack, impersonation attack, privileged insider attack, replay attack, off-line password guessing attack, theft attack, session key recovery attack, denial of service attack, and cluster head capture attack. However, we find some weaknesses of his scheme in this article. We show that their scheme is vulnerable to off-line password guessing with smart card stolen attack.