Revocable Identity-based Encryption from Codes with Rank Metric

In this paper, we present an identity-based encryption scheme from codes with efficient key revocation. Recently, in Crypto 2017, Gaborit et al. proposed a first identity-based encryption scheme from codes with rank metric, called RankIBE. To extract the decryption key from any public identity, they constructed a trapdoor function which relies on RankSign, a signature scheme proposed by Gaborit et al. in PQCrypto 2014. We adopt the same trapdoor function to add efficient key revocation functionality in the RankIBE scheme. Our revocable IBE scheme from codes with rank metric makes use of a binary tree data structure to reduce the amount of work in terms of key updates for the key authority. The total size of key updates requires logarithmic complexity in the maximum number of users and linear in the number of revoked users. We prove that our revocable IBE scheme is selective-ID secure in the random oracle model, under the hardness of three problems: the Rank Syndrome Decoding (RSD) problem, the Augmented Low-Rank Parity Check Code (LRPC+) problem, and the Rank Support Learning (RSL) problem

A Performance Evaluation of Pairing-Based Broadcast Encryption Systems

In a broadcast encryption system, a sender can encrypt a message for any subset of users who are listening on a broadcast channel. The goal of broadcast encryption is to leverage the broadcasting structure to achieve better efficiency than individually encrypting to each user; in particular, reducing the bandwidth (i.e., ciphertext size) required to transmit securely, although other factors such as public and private key size and the time to execute setup, encryption and decryption are also important. In this work, we conduct a detailed performance evaluation of eleven public-key, pairing-based broadcast encryption schemes offering different features and security guarantees, including public-key, identity-based, traitor-tracing, private linear and augmented systems. We implemented each system using the MCL Java pairings library, reworking some of the constructions to achieve better efficiency. We tested their performance on a variety of parameter choices, resulting in hundreds of data points to compare, with some interesting results from the classic Boneh-Gentry-Waters scheme (CRYPTO 2005) to Zhandry\u27s recent generalized scheme (CRYPTO 2020), and more. We combine this performance data and knowledge of the systems\u27 features with data we collected on practical usage scenarios to determine which schemes are likely to perform best for certain applications, such as video streaming services, online gaming, live sports betting and smartphone streaming. This work can inform both practitioners and future cryptographic designs in this area

Lattice-based Identity-Based Broadcast Encryption Scheme

Motivated by the lattice basis delegation technique due to [8], we propose an adaptively secure identity-based broadcast encryption(IBBE) scheme based on the hard worst-case lattice problems. Our construction can be generalized to obtain a hierarchical IBBE (HIBBE) scheme easily. To the best of the authors\u27 knowledge, our construction and its variants constitute the first adaptively secure IBBE schemes from lattices, which are believed secure in the post-quantum environment