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Security and Communication Networks

More efficient CCA‐secure unidirectional proxy re‐encryption schemes without random oracles

Hongbing Wang, Zhenfu Cao

Published Jun 5, 2012• 7 citations
Publisher

Abstract

ABSTRACT In this paper, we present a more efficient chosen‐ciphertext secure proxy re‐encryption scheme in the standard model with less ciphertext size and without any strong unforgeable one‐time signature. Our scheme is unidirectional and single‐hop. The security of our scheme is under the reasonable complexity assumption—the decisional bilinear Diffie–Hellman assumption in bilinear groups. There are no proxy re‐encryption schemes achieving chosen‐ciphertext security in the standard model without a strong unforgeable one‐time signature in the literature. Copyright © 2012 John Wiley & Sons, Ltd.

DOI
10.1002/sec.552

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ABSTRACT In this paper, we present a more efficient chosen‐ciphertext secure proxy re‐encryption scheme in the standard model with less ciphertext size and without any strong unforgeable one‐time signature. Our scheme is unidirectional and single‐hop. The security of our scheme is under the reasonable complexity assumption—the decisional bilinear Diffie–Hellman assumption in bilinear groups. There are no proxy re‐encryption schemes achieving chosen‐ciphertext security in the standard model without a strong unforgeable one‐time signature in the literature. Copyright © 2012 John Wiley & Sons, Ltd.
Proxy re-encryption, introduced by Blaze et al. in 1998, allows a proxy to transform a ciphertext computed under Alice's public key into one that can be opened under Bob's decryption key. An open problem of constructing (bidirectional or unidirectional) IND-PRE-CCA2 secure proxy re-encryption scheme in the standard model yet without pairings was left until now. In this paper, based on Hanaoka's efficient chosen ciphertext secure public key encryption under the computational Diffie-Hellman assumption, we try to solve this open problem by presenting two new bidirectional proxy re-encryption schemes, which are restricted IND-PRE-CCA2 secure without pairing nor random oracle.
In 1998, Blaze, Bleumer and Strauss introduced a cryptographic primitive called proxy re-encryption in which a proxy can transform-without seeing the plaintext-a ciphertext encrypted under one key into an encryption of the same plaintext under another key. The concept has recently drawn renewed interest. Notably, Canetti and Hohenberger showed how to properly define (and realize) chosen-ciphertext security for the primitive. Their system is bidirectional as the translation key allows converting ciphertexts in both directions. This paper presents the first unidirectional proxy re-encryption schemes with chosen-ciphertext security in the standard model (i.e., without the random oracle idealization). The first system provably fits a unidirectional extension of the Canetti-Hohenberger security model. As a second contribution, the paper considers a more realistic adversarial model where attackers may choose dishonest users' keys on their own. It is shown how to modify the first scheme to achieve security in the latter scenario. At a moderate expense, the resulting system provides additional useful properties such as non-interactive temporary delegations. Both constructions are efficient and rely on mild complexity assumptions in bilinear groups. Like the Canetti-Hohenberger scheme, they meet a relaxed flavor of chosen-ciphertext security introduced by Canetti, Krawczyk and Nielsen.
Proxy Re-Encryption was introduced by Blaze, Bleumer and Strauss to efficiently solve the problem of delegation of decryption rights. In proxy re-encryption, a semi-honest proxy transforms a ciphertext intended for Alice to a ciphertext of the same message for Bob without learning anything about the underlying message. From its introduction, several proxy re-encryption schemes in the Public Key In-frastructure (PKI) and Identity (ID) based setting have been proposed. In practice, systems in the public key infrastructure suffer from the certificate management problem and those in identity based setting suffer from the key escrow problem. Certificateless Proxy Re-encryption schemes enjoy the advantages provided by ID-based constructions without suffering from the key escrow problem. In this work, we construct the first unidirectional, single-hop CCA-secure certificateless proxy re-encryption scheme without pairing by extending the PKI based construction of Chow et al. proposed in 2010. We prove its security in the random oracle model under the Computational Diffie-Hellman (CDH) assumption. Prior to this work, the only secure certificateless proxy re-encryption scheme is due to Guo et al. proposed in 2013 using bilinear pairing. The construction proposed in this work is more efficient than that system and its security relies on more standard assumptions. We also show that the recently proposed construction of Yang et al. is insecure with respect to the security model considered in this work.
Abstract Several generic methods exist for achieving chosen‐ciphertext attack (CCA)‐secure public‐key encryption schemes from weakly secure cryptosystems, such as the Fujisaki–Okamoto and REACT transformations. In the context of proxy re‐encryption (PRE), it would be desirable to count on analogous constructions that allow PRE schemes to achieve better security notions. In this paper, we study the adaptation of these transformations to proxy re‐encryption and find both negative and positive results. On the one hand, we show why it is not possible to directly integrate these transformations with weakly secure PRE schemes because of general obstacles coming from both the constructions themselves and the security models, and we identify 12 PRE schemes that exhibit these problems. On the other hand, we propose an extension of the Fujisaki–Okamoto transformation for PRE, which achieves a weak form of CCA security in the random oracle model, and we describe the sufficient conditions for applying it. Copyright © 2016 John Wiley & Sons, Ltd.
Up to now, it is still an open question of how to construct a chosen-ciphertext secure unidirectional proxy re-encryption scheme in the adaptive corruption model. To address this problem, we propose a new unidirectional proxy re-encryption scheme, and prove its chosen-ciphertext security in the adaptive corruption model without random oracles. Compared with the best known unidirectional proxy re-encryption scheme proposed by Libert and Vergnaud in PKC’08, our scheme enjoys the advantages of both higher efficiency and stronger security.