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Cryptanalysis and enhancement of a distributed fine-grained access control in wireless sensor networks

Fine-grained access control is used to assign unique access privilege to a particular user for accessing the relevant information. Recently, Yu et al. and Ruj et al. proposed a couple of fine grained access control schemes using public key cryptography. These schemes exploit and maneuver the concept of KP-ABE and a cryptographic technique based on bilinear pairing on elliptive curve groups. In this paper, we first show that though these schemes are efficient, but both schemes suffer from some fatal weakness such as vulnerability against an insider attack, specifically key abuse attacks by the genuine users. Therefore, a user with lower access privilege can access the secret data sent for a user of higher access privilege. This contradicts the basic objective of fine grained access control. Also, information sent for a particular user can be revealed to an adversary. In order to remedy that weakness, we propose some simple countermeasures to prevent key-abuse insider attack while the merits of existing fine grained access control scheme are left unchanged. Further, our scheme is unconditionally secure against various attacks such as man-in-the-middle attack, replay attack and denial of service attack. While providing these extra security features, our scheme incurs no such extra communication, computation or storage overhead as compared to the existing schemes.