Secure and {\sl Practical} Identity-Based Encryption

TL;DR

This paper introduces a practical identity-based encryption scheme with significantly reduced public key size, maintaining semantic security and addressing an open question in the field.

Contribution

It presents a new variant of Waters' IBE scheme with smaller public keys and proven security, advancing practical deployment of IBE systems.

Findings

Public key size reduced to a few kilobytes

Scheme remains semantically secure in the standard model

First fully secure practical IBE scheme

Abstract

In this paper, we present a variant of Waters' Identity-Based Encryption scheme with a much smaller public-key size (only a few kilobytes). We show that this variant is semantically secure against passive adversaries in the standard model.\smallskip In essence, the new scheme divides Waters' public key size by a factor $\ell$ at the cost of (negligibly) reducing security by $\ell$ bits. Therefore, our construction settles an open question asked by Waters and constitutes the first fully secure {\sl practical} Identity-Based Encryption scheme