key: 2015-ciphertext-plus-proof-of-knowledge-is-NM-CPA
type: inproceedings
title: NM-CPA secure encryption with proofs of plaintext knowledge
authors:
  - Ben Smyth
  - Yoshikazu Hanatani
  - Hirofumi Muratani
year: 2015
month: 6
booktitle: "IWSEC'15: 10th International Workshop on Security"
series: LNCS
volume: "9241"
publisher: Springer
doi: 10.1007/978-3-319-22425-1_8
description: >-
  This paper presents a construction for NM-CPA ciphertexts which prove plaintext knowledge.
  Applications include ballot secrecy proofs in schemes such as Helios.
keywords: >-
  asymmetric encryption, ballot secrecy, chosen plaintext attacks, elections, election scheme,
  electronic voting, e-voting, Helios, homomorphic encryption, indistinguishability,
  non-malleability, privacy, secrecy
abstract: >-
  NM-CPA secure asymmetric encryption schemes which prove plaintext knowledge are sufficient for
  secrecy and verifiability in some domains, for example, ballot secrecy and end-to-end
  verifiability in electronic voting. In these domains, some applications derive encryption schemes
  by coupling malleable IND-CPA secure ciphertexts with proofs of plaintext knowledge, without
  evidence that the sufficient condition is satisfied nor an independent security proof.
  Consequently, it is unknown whether these applications satisfy the desired secrecy and
  verifiability properties. In this paper, we propose a generic construction for such a coupling and
  prove that our construction produces NM-CPA secure encryption schemes which prove plaintext
  knowledge. Accordingly, we facilitate the development of applications satisfying their secrecy and
  verifiability objectives and, moreover, we make progress towards security proofs for existing
  applications.
supersededby:
  - key: 2018-ballot-secrecy-from-NM-CPA
    text: extension