Achieving Effective Cloud Search Services:
Multi-keyword Ranked Search over Encrypted
Cloud Data Supporting Synonym Query
Zhangjie Fu, Member, IEEE, Xingming Sun, Senior Member, IEEE, Nigel Linge, Lu Zhou
Abstract — In recent years, consumer-centric cloud
computing paradigm has emerged as the development of
smart electronic devices combined with the emerging cloud
computing technologies. A variety of cloud services are
delivered to the consumers with the premise that an effective
and efficient cloud search service is achieved. For consumers,
they want to find the most relevant products or data, which is
highly desirable in the “pay-as-you use” cloud computing
paradigm. As sensitive data (such as photo albums, emails,
personal health records, financial records, etc.) are encrypted
before outsourcing to cloud, traditional keyword search
techniques are useless. Meanwhile, existing search
approaches over encrypted cloud data support only exact or
fuzzy keyword search, but not semantics-based multi-keyword
ranked search. Therefore, how to enable an effective
searchable system with support of ranked search remains a
very challenging problem. This paper proposes an effective
approach to solve the problem of multi-keyword ranked
search over encrypted cloud data supporting synonym
queries. The main contribution of this paper is summarized in
two aspects: multi-keyword ranked search to achieve more
accurate search results and synonym-based search to support
synonym queries. Extensive experiments on real-world dataset
were performed to validate the approach, showing that the
proposed solution is very effective and efficient for multi-
keyword ranked searching in a cloud environment
1
.
Index Terms — Cloud computing, consumer-centric cloud,
keyword search, ranked search.
I. INTRODUCTION
In recent years, many consumer electronic devices (e.g.
Smartphone) with support of high speed computing combined
1
This work is supported by the NSFC(61232016, 61173141, 61173142,
61173136, 61103215, 61373132, 61373133, 61300238), GYHY201206033,
201301030, 2013DFG12860, BC2013012, Jiangsu Provincial Natural Science
Foundation (BK20131004) and PAPD fund.
Z. J. Fu is with the School of Computer and Software & Jiangsu
Engineering Centre of Network Monitoring, Nanjing University of
Information Science and Technology, Nanjing, 210044, CHINA (e-mail:
wwwfzj@126.com).
X. M. Sun is with the Jiangsu Engineering Centre of Network Monitoring,
Nanjing University of Information Science and Technology, Nanjing, 210044,
CHINA (e-mail: sunnudt@163.com).
N. Linge is with the School of Computing, Science and Engineering,
University of Salford, Salford, M5 4WT, UK.(e-mail: n.linge@salford.ac.uk).
L. Zhou is with the School of Computer and Software, Nanjing University
of Information Science and Technology, Nanjing, 210044, CHINA (e-mail:
zl_0713@163.com).
with the emerging cloud computing paradigm provide a variety
of service to the consumers. Cabarcos P.A. et al [1] proposed a
novel middleware architecture that allows sessions initiated from
one device to be seamlessly transferred to a second one under a
cloud computing environment. Díaz-Sánchez D. et al [2]
presented a cloud computing middleware Media Cloud for set-
top boxes for classifying, searching, and delivering media inside
home network and across the cloud. Seung G. L. et al [3]
proposed a personalized DTV program recommendation system
under a cloud computing environment. The system can analyze
and use the viewing pattern of consumers to personalize the
program recommendations.
However, all these services are likely to be available to
consumers only with the premise that an effective and efficient
cloud search service is achieved. Consumers want to find the
most relevant products or data, which is highly desirable in the
“pay-as-you use” cloud computing paradigm.
One hand, consumer-centric cloud computing [4] is a new
model of enterprise-level IT infrastructure that provides on-
demand high quality applications and services from a shared pool
of configuration computing resources for consumers. On the
other hand, some problems may be caused in this circumstance
since the Cloud Service Provider (CSP) possesses full control of
the outsourced data. There may exist unauthorized operation [5]
on the outsourced data on account of curiosity or profit. So
sensitive data are encrypted before outsourcing to the cloud.
However, encrypted data make the traditional data utilization
services based on plaintext keyword search useless. The simple
and awkward method of downloading all the data and decrypting
locally is obviously impractical, because the authorized cloud
consumers must hope to search their interested data rather than
all the data. Hence, it is an especially important thing to explore
an effective search service over encrypted outsourced data.
Existing search approaches cannot accommodate such
requirements like ranked search, multi-keywords search,
semantics-based search etc. The ranked search enables cloud
customers to find the most relevant information quickly. Ranked
search can also reduce network traffic as the cloud server sends
back only the most relevant data. Multi-keyword search is also
very important to improve search result accuracy as single
keyword search often return coarse search results. In the real
search scenario, it is quite common that cloud customers’
searching input might be the synonyms of the predefined
keywords, not the exact or fuzzy matching keywords due to the
IEEE Transactions on Consumer Electronics, Vol. 60, No. 1, February 2014