A continuous leakage-amplified IBE scheme with perfect key update

Abstract

In the practical deployment of cryptographic solutions, diverse applications pose unique challenges in terms of leakage resilience. The one-size-fits-all approach of traditional cryptographic primitives and fixed leakage-resilient ability often fails to satisfy the nuanced security demands of different scenarios. Recognizing this, the concept of a continuous Identity-based Encryption (IBE) scheme has been introduced. This innovative approach allows for the dynamic adjustment of private key lengths to tailor the system’s resistance to various leakage attacks, based on the specific needs of an application. Despite the strides made, the existing implementations of this scheme exhibit limitations, particularly in the aspect of key updates. The current method for key updates is incomplete, only updating some elements of the key. This process relies on a trapdoor mechanism, which results in suboptimal storage efficiency. This paper introduces a new continuous leakage amplified IBE scheme to address these shortcomings. This improved model features a comprehensive key update mechanism that enables users to refresh every element of the private key without utilizing a trapdoor. Our analysis confirms that this enhanced IBE scheme stands out for its security, efficiency, and practicality. Moreover, in pursuit of optimizing performance, we present a novel general construction. This construction illustrates that it is feasible to construct an IBE scheme resilient against chosen-ciphertext attacks, equipped with an impeccable update function, by building upon any semantically secure IBE scheme.