Comments on IMBAS: identity-based multi-user broadcast authentication in wireless sensor networks

ABSTRACT In 2008, Cao et al. proposed an identity‐based multi‐user broadcast authentication scheme (called IMBAS) for wireless sensor networks. The IMBAS consists of one elliptic curve‐based signature scheme, called variant of Bellare‐Namprempre‐Neven' Identity‐Based Signature (vBNN‐IBS), for user broadcast authentication; a new Schnorr signature with partial message recovery for sink broadcast authentication; and a password‐based private key protection to eliminate the threat caused by possible user device compromise. Compared with its counterparts, IMBAS owns better performance in terms of security, scalability, and efficiency. Unfortunately, this letter will show that (1) the password‐based protection scheme and the vBNN‐IBS scheme are not secure—a compromised user device will disclose the user private key—and (2) the new Schnorr signature with partial message recovery is vulnerable to existential forgery attack. Copyright © 2012 John Wiley & Sons, Ltd. The identity‐based multi‐user broadcast authentication (called IMBAS) scheme for wireless sensor networks by Cao et al. is a very promising solution in terms of its scalability and efficiency. This article shows the security weaknesses and proposes our improvements, which are based on existing primitives that have been formally proved and ratified as standards. This approach ensures the security of the proposed solutions.