Adaptively Secure Distributed Broadcast Encryption with Linear-Size Public Parameters

TL;DR

This paper introduces a new distributed broadcast encryption scheme that achieves constant size ciphertexts and private keys, with linear size public parameters, and proves its adaptive security under static assumptions.

Contribution

It presents the first DBE scheme with linear size public parameters that is adaptively secure under static assumptions in composite-order bilinear groups.

Findings

Achieves constant size ciphertexts and private keys.

Public parameters grow linearly with the number of users.

Proven secure under static assumptions in composite-order bilinear groups.

Abstract

Distributed broadcast encryption (DBE) is a variant of broadcast encryption (BE) that can efficiently transmit a message to a subset of users, in which users independently generate user private keys and user public keys instead of a central trusted authority generating user keys. In this paper, we propose a DBE scheme with constant size ciphertexts, constant size private keys, and linear size public parameters, and prove the adaptive security of our DBE scheme under static assumptions in composite-order bilinear groups. The previous efficient DBE schemes with constant size ciphertexts and constant size private keys are proven secure under the $q$-Type assumption or have a drawback of having quadratic size public parameters. In contrast, our DBE scheme is the first DBE scheme with linear size public parameters proven adaptively secure under static assumptions in composite-order bilinear groups.