Cryptology ePrint Archive: Report 2016/327

Proxy Re-Encryption Schemes with Key Privacy from LWE

Le Trieu Phong and Lihua Wang and Yoshinori Aono and Manh Ha Nguyen and Xavier Boyen

Abstract: Proxy re-encryption (PRE) is a cryptographic primitive in which a proxy can transform Alice's ciphertexts into ones decryptable by Bob. Key-private PRE specifies an additional level of security, requiring that proxy keys leak no information on the identities of Alice and Bob. In this paper, we build two key-private PRE schemes: (1) we propose a CPA-secure key-private PRE scheme in the standard model, and (2) we then transform it into a CCA-secure scheme in the random oracle model. Both schemes enjoy following properties: both are uni-directional and the CPA-secure one is a multi-hop scheme. In addition, the security of our schemes is based on the hardness of the standard Learning-With-Errors (LWE) problem, itself reducible from worst-case lattice hard problems that are conjectured immune to quantum cryptanalysis, or ``post-quantum''. We implement the CPA-secure scheme and point out that, among many applications, it can be sufficiently used for the practical task of key rotation over encrypted data.

Category / Keywords: public-key cryptography /

Original Publication (with major differences): INDOCRYPT 2013

Date: received 24 Mar 2016, last revised 25 Jul 2017

Contact author: phong at nict go jp

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Version: 20170726:051449 (All versions of this report)

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