@article{Kandele_Paul_2018, title={Key Assignment Scheme with Authenticated Encryption}, volume={2018}, url={https://tosc.iacr.org/index.php/ToSC/article/view/7365}, DOI={10.13154/tosc.v2018.i4.150-196}, abstractNote={<p>The <em>Key Assignment Scheme (KAS)</em> is a well-studied cryptographic primitive used for <em>hierarchical access control (HAC)</em> in a multilevel organisation where the classes of people with higher privileges can access files of those with lower ones. Our first contribution is the formalization of a new cryptographic primitive, namely, <em>KAS-AE</em> that supports the aforementioned <em>HAC</em> solution with an additional <em>authenticated encryption</em> property. Next, we present three efficient <em>KAS-AE</em> schemes that solve the <em>HAC</em> and the associated <em>authenticated encryption</em> problem more efficiently – both with respect to time and memory – than the existing solutions that achieve it by executing <em>KAS</em> and <em>AE</em> separately. Our first <em>KAS-AE</em> construction is built by using the cryptographic primitive <em>MLE</em> (EUROCRYPT 2013) as a black box; the other two constructions (which are the most efficient ones) have been derived by cleverly tweaking the hash function <em>FP</em> (Indocrypt 2012) and the authenticated encryption scheme <em>APE</em> (FSE 2014). This high efficiency of our constructions is critically achieved by using two techniques: design of a mechanism for <em>reverse decryption</em> used for reduction of time complexity, and a novel key management scheme for optimizing storage requirements when organizational hierarchy forms an arbitrary access graph (instead of a linear graph). We observe that constructing a highly efficient <em>KAS-AE</em> scheme using primitives other than <em>MLE</em>, <em>FP</em> and <em>APE</em> is a non-trivial task. We leave it as an open problem. Finally, we provide a detailed comparison of all the <em>KAS-AE</em> schemes.</p>}, number={4}, journal={IACR Transactions on Symmetric Cryptology}, author={Kandele, Suyash and Paul, Souradyuti}, year={2018}, month={Dec.}, pages={150–196} }