On the Insecurity of Proactive RSA in the URSA Mobile Ad Hoc Network Access Control Protocol
Access control is the fundamental security service in ad hoc groups. It is needed not only to prevent unauthorized entities from joining the group, but also to bootstrap other security services. Luo, et al. proposed a set of protocols for providing Ubiquitous and Robust Access control (called URSA1) in mobile ad hoc networks without relying on a centralized authority. The URSA protocol relies on the new proactive RSA signature scheme, which allows members in an ad hoc group to make access control decisions in a distributed manner. The proposed proactive RSA signature scheme is assumed secure as long as no more than an allowed threshold of participating members is simultaneously corrupted at any point in the lifetime of the scheme.