An Improved Cloud-Based Revocable
Identity-Based Proxy Re-encryption Scheme
Changji Wang
1,2(
B
)
, Jian Fang
2,3
,andYuanLi
2,3
1
School of Software, Yunnan University, Kunming 650500, China
wchangji@gmail.com
2
Guangdong Key Laboratory of Information Security Technology,
Sun Yat-sen University, Guangzhou 510275, China
3
School of Information Science and Technology, Sun Yat-sen University,
Guangzhou 510275, China
Abstract. Key revocation and ciphertext update are two prominent
security requirements for identity-based encryption systems from a prac-
tical view. Several solutions to offer efficient key revocation or cipher-
text update for identity-based encryption systems have been proposed in
the literature. However, how to achieve both key revocation and cipher-
text update functionalities simultaneously in identity-based encryption
systems is still an open problem. Recently, Liang et al. introduce the
notion of cloud-based revocable identity-based proxy re-encryption (CR-
IB-PRE) scheme with the aim to achieve both ciphertext update and
key revocation functionalities, and present a CR-IB-PRE scheme from
bilinear pairings. In this paper, we first showed Liang et al.’s scheme has
serious security pitfalls such as re-encryption key forgery and collusion
attack, which lead to revoked users can decrypt any ciphertext regard-
ing their identities at any time period. We then redefined the syntax
and security model of CR-IB-PRE scheme and proposed an improved
CR-IB-PRE scheme from bilinear pairings. The improved scheme not
only achieves collusion resistance, but also takes lower decryption com-
putation and achieves constant size re-encrypted ciphtertext. Finally,
we proved the improved CR-IB-PRE scheme is adaptively secure in the
standard model under DBDH assumption.
Keywords: Identity-based encryption
· Proxy re-encryption · Key
revocation
· Ciphertext update · Cloud computing
1 Introduction
The concept of identity-based public key cryptography (ID-PKC) was originally
introduced by Shamir [1] to avoid cumbersome certificate management. In an
identity-based crypto-system, users do not need to pre-compute public key and
private key pairs and obtain certificates for their public keys. Instead, users’ iden-
tifiers information such as email addresses, telephone numbers or social security
numbers can be used as users’ public keys, while private keys are derived at
c
Springer-Verlag Berlin Heidelberg 2015
W. Niu et al. (Eds.): ATIS 2015, CCIS 557, pp. 14–26, 2015.
DOI: 10.1007/978-3-662-48683-2
2
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