Puncturable Encryption: A Generic Construction from Delegatable Fully Key-Homomorphic Encryption

TL;DR

This paper introduces a generic construction of puncturable encryption using fully key-homomorphic encryption with key delegation, providing the first post-quantum secure PE instantiation based on LWE, and discusses extending its capabilities.

Contribution

It presents a novel generic PE construction from DFKHE, achieving post-quantum security based on LWE, and explores potential for supporting unlimited ciphertext tags.

Findings

Achieves selective security under CPA in the standard model.

First post-quantum secure PE instantiation based on LWE.

Framework potentially supports unbounded ciphertext tags.

Abstract

Puncturable encryption (PE), proposed by Green and Miers at IEEE S&P 2015, is a kind of public key encryption that allows recipients to revoke individual messages by repeatedly updating decryption keys without communicating with senders. PE is an essential tool for constructing many interesting applications, such as asynchronous messaging systems, forward-secret zero round-trip time protocols, public-key watermarking schemes and forward-secret proxy re-encryptions. This paper revisits PEs from the observation that the puncturing property can be implemented as efficiently computable functions. From this view, we propose a generic PE construction from the fully key-homomorphic encryption, augmented with a key delegation mechanism (DFKHE) from Boneh et al. at Eurocrypt 2014. We show that our PE construction enjoys the selective security under chosen plaintext attacks (that can be converted into the adaptive security with some efficiency loss) from that of DFKHE in the standard model. Basing on the framework, we obtain the first post-quantum secure PE instantiation that is based on the learning with errors problem, selective secure under chosen plaintext attacks (CPA) in the standard model. We also discuss about the ability of modification our framework to support the unbounded number of ciphertext tags inspired from the work of Brakerski and Vaikuntanathan at CRYPTO 2016.