Proxy Provable Data
Possession in Public Clouds
Huaqun Wang
Abstract—Recently, cloud computing rapidly expands as an alternative to conventional computing due to it can provide a flexible,
dynamic and resilient infrastructure for both academic and business environments. In public cloud environment, the client moves its
data to public cloud server (PCS) and cannot control its remote data. Thus, information security is an important problem in public cloud
storage, such as data confidentiality, integrity, and availability. In some cases, the client has no ability to check its remote data
possession, such as the client is in prison because of committing crime, on the ocean-going vessel, in the battlefield because of the
war, and so on. It has to delegate the remote data possession checking task to some proxy. In this paper, we study proxy provable data
possession (PPDP). In public clouds, PPDP is a matter of crucial importance when the client cannot perform the remote data
possession checking. We study the PPDP system model, the security model, and the design method. Based on the bilinear pairing
technique, we design an efficient PPDP protocol. Through security analysis and performance analysis, our protocol is provable secure
and efficient.
Index Terms—Cloud computing, PPDP, integrity checking, provable security, bilinear pairings
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1INTRODUCTION
A
LONG with the development of network and computer
technology, cloud computing has become a reality. In
the development of information technology, it is always an
important problem to increase capacity or add capabilities
on the fly without investing in new infrastructure, training
new personnel, or licensing new software. Cloud comput-
ing can solve this problem. Since cloud computing can
provide a flexible, dynamic, resilient, and cost-effective
infrastructure for both academic and business environ-
ments, it rapidly expands as an alternative to conventional
office-based computing. Terminal clients can access the
cloud-based applications via a Web browser or a light-
weight desktop or mobile application while the business
software and data are stored on the cloud servers at a
remote location. Cloud service providers (CSPs) manage the
PCS and offer the services as the following three categories:
software as a service, platform as a service, and infra-
structure as a service. Cloud computing logical diagram can
be shown in Fig. 1.
Generally, cloud computing consists of three different
types: public cloud, private cloud, hybrid cloud. In public
cloud, cloud service provider makes resources, such as
applications and storage, available to the general public via
Internet or other access interfaces. Public cloud services
may be free or offered on a pay-per-usage model. There
exist some benefits to use public cloud services which can
be depicted as follows: easy and inexpensive setup because
hardware, application and bandwidth costs are covered by
the provider; scalability to meet needs; no wasted resources
because you pay for what you use, and so on. Public clouds
are external or publicly available cloud environments that
can be accessed by multiple clients, whereas private clouds
only can be accessed by particular organizations. Hybrid
cloud environment comprises public cloud and private
cloud. Public cloud computing logical diagram can be
shown in Fig. 2. Since the clients cannot control their remote
data, the CSPs are more responsible for the security and
privacy of application services, more so in public clouds
than private clouds. In private clouds, the client organiza-
tions might have stringent secur it y r equi rem ents and
provide the required enforcement services. We only focus
on the public cloud computing environment.
In public clouds, there is a “visibility gap” between the
CSP and the client, in which they cannot see into each
other’s management, operation, technical infrastructure,
and procedures. The client cannot control his own remote
data. This situation incurs some security problems. It is an
important problem to ensure remote data possession in
public clouds. Untrusted PCS may modify the client’s data
to save the storage space or other aims. Or, some faults
make some data lost. Thus, it is necessary to study remote
data possession in public clouds.
1.1 Motivation
In public cloud environment, most clients will access the
PCS by Internet. After the clients stores their massive data
on the remote untrusted PCS, they will check their remote
data’ integrity at regular intervals. To improve security and
save the fee, the cloud service providers will add some
security countermeasures, such as offline backup. To
restrict malicious and frequent access, PCS will require
the clients to input the corresponding verification code.
After that, the clients can perform the integrity checking
protocol. This means that every client has to perform the
integrity checking protocol b y himself. When CSP’s
IEEE TRANSACTIONS ON SERVICES COMPUTING, VOL. 6, NO. 4, OCTOBER-DECEMBER 2013 551
. The author is with the School of Information Engineering, Dalian Ocean
University, Dalian 116023, P.R. China and with the State Key Laboratory
of Integrated Services Networks, Xidian University, Xi’an 710071, P.R.
China. E-mail: wanghuaqun@yahoo.com.cn.
Manuscript received 25 Aug. 2012; revised 28 Oct. 2012; accepted 3 Nov.
2012; published online 16 Nov. 2012.
For information on obtaining reprints of this article, please send e-mail to:
tsc@computer.org, and reference IEEECS Log Number TSC-2012-08-0096.
Digital Object Identifier no. 10.1109/TSC.2012.35.
1939-1374/13/$31.00 ß 2013 IEEE Published by the IEEE Computer Society