Abstract: Cloud
Computing is a new technology that allows access to applications as utilities
over the internet. Cloud computing environment provides a great flexibility and
availability of computing resources at a lower cost. However, it brings new
security concerns mainly when users understand exactly how a process is
running. One of the main important challenges in cloud computing is data
security, as users need to access data they share securely. So the main problem
is how to employ an effective authentication procedure for ensuring data
security and preventing unauthorized users to access the authorized user’s
data. This paper identifies the security issues of single level authentication
and the problem of single password. This study proposed a new security
mechanism for cloud computing based on multilevel authentication. The proposed
scheme aimed to enhance the security and authentication process in cloud
computing. The proposed scheme consists of three level of authentication, and
the data will be splitting on this level depending on the sensitivity to
confidential (C), secret (S), and top secret (TS). Data at level (C) have the
lowest sensitivity. The user at this level has single textual password to
access this level data. The user at level (S) has two passwords, textual and
biometrics password to access this level and the lower level. User at level
(TS) has three password textual, biometrics password and image sequencing
password. The data at this level is the more sensitive data so it is encrypted
using RSA algorithm before storing in cloud database. The results of the
proposed multilevel authentication for cloud computing were promising.

Keywords: : Authentication,
Cloud Computing, Multilevel, Security.




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Cloud computing is a new technology that move the
computation process from desktop computers to cloud providers through the
internet1. Cloud computing provides computer infrastructures, platforms and
software as services. This model decreases the computation cost and make
organizations focus on their businesses. Three types of services are offered by
cloud providers. These types are Software as a Service (SaaS), Platform as a
Service (PaaS), and Infrastructure as a Service (IaaS). In Software as a Service
(SaaS), cloud providers provide software applications as services for clients.
In Platform as a Service (PaaS) cloud providers provide platforms for clients
so clients can develop their own applications on those platforms. In
Infrastructure as a Service (IaaS), cloud clients request computer hardware
such as processing unit, storage devices and network components as services2,

One of the main benefits of cloud computing is
releasing cloud clients from the concerns about processing details and how data
will be handled. However, moving to cloud brings new challenges and concerns
regarding security and privacy 4-6. Authentication of cloud users represents
a critical issue in cloud computing security. Several cloud providers use
single level authentication scheme as shown in Figure 1, such as simple text
password for clients to access cloud services.

Figure1. Single Level of Authentication for Cloud Computing

Other cloud providers employ graphical password
third party authentication and biometric authentication. However, most of these
models have limitations and do not work well if they used in single level
authentication scheme. So the main problem challenge in cloud computing is how
to perform a proper authentication procedures for ensuring data security and
preventing unauthorized users to access the confidential data. The objective of
this research is to propose a new model for cloud security that enhances
authentication system based on multilevel authentication.


This paper has six sections. Section two describes
the related works. Section three illustrates the multilevel security. Section
four describes the proposed scheme. Section five presents the results and
discussions and we concluded in section six.



Yassin, A. A., H. Jin, et al in 7 developed a new a scheme for cloud
authentication that depends on One-Time Password (OTP), Asymmetric
Scalar-product Preserving Encryption (ASPE) and RSA digital signature as two
factors. The model proposed in 8 is based on strict authentication system by
introducing multi-level authentication technique which generates and
authenticates the password in multiple levels to access the cloud services. The
limitation of these methods is they use the same password at different level of
authentication. The researchers in 9 apply a new framework for secure cloud
authentication using tenant’s identification model. To overcome
Denial-of-Service attack and to insecure password change Jaidhar C. D proposed
an enhanced mutual authentication scheme for cloud architecture 10.


Bo Wang, HongYu Xing 4, he mainly focused on the research of the
application of cloud computing in education informatization. Firstly, the
traditional computer technologies, including the virtualization, network storage
technology, distributed computing, parallel computing technology, network
technology and automation techniques etc. have made a tremendous development.
The concept of cloud computing was jointly proposed by Google and IBM in 2007.
Secondly, cloud computing is of significant importance to adapt to the
development of information technology in education. Furthermore, it plays an
important role in creating a flexible, unified and open platform for education
information, sharing of educational resources, and alleviating the information
gap between different areas of education. Finally, after the analysis of the
educational information technology in today’s China, through the study of the
basic concepts of cloud computing technology, core technology and system
architecture, they discusses cloud computing applying in education information.

Cavoukian 7, implemented security as a service in the Cloud using a
discretion algorithm and also implementing an intrusion detection system for
the Cloud. To protect and mitigate the privacy and security attacks on the
Cloud. Currently, there is on-going research on how to protect the
confidentiality and security of data stored in the Cloud.



Multilevel security is a security discipline in
which more than one security control is used to protect system security.
Mandatory access control (MAC) is a scheme that prevents unauthorized clients
from accessing objects that have sensitive information 11.

3.1 Multilevel Database Security


One of the main applications
for mandatory access control is multilevel security (MLS), which has been built
mainly for network, database and computer systems that have highly sensitive
information 12.

Each item in multilevel
security is defined as an object and has a security class level. Moreover, each
user is considered as a subject and also has a security class level. In
multilevel security a label is the class level of an object or a subject X and
is denoted as L(X). Different access control are available for multi level
security, Bell–LaPadula is a main one 11. Bell–LaPadula model has three
rules. The first one is: a user x is granted a read access to an object o only
if L (x) is higher than or equal to L (o). The second rule is: a user x is
granted a write access to an object o only if L(x) is less than or equal to
L(o). The third rule is: a user x is granted a write access to an object o only
if L(x) is equal to L (o). Bell–LaPadula model aims to prevent a subject with
lower level from accessing a higher level object and this called no read-up


Multilevel Authentication System


Cloud providers offer
internet based on-demand data storage services to clients or tenants. In this
scheme, client’s databases are stored remotely in the cloud provider data
centers. The security of client’s databases is based on the security controls
employed by the cloud providers 13. Cloud providers use single level
authentication to allow clients access their data securely. Simple text
password, biometric authentication, third party authentication, and graphical
password are the main single level authentication used in cloud computing 14.
Each single level authentication scheme has limitations and drawbacks if scheme
is used alone. Textual password authentication model is easy to break and
vulnerable to dictionary and brute force attacks. For small cloud services,
third party authentication is not recommended. Graphical passwords are based on
the idea that users can recall and recognize pictures better than words.
Nevertheless, some graphical password mechanism is time and memory consuming.
Bio-metric authentications scheme such as, fingerprints, hand geometry, face
recognition, and voice recognition has been used for cloud services
authentication. One of the key challenge and disadvantage of applying
biometrics is its intrusiveness upon a client’s personal characteristic.
Furthermore, biometric scheme require a special scanning device to validate
users characteristic, which is not appropriate for internet users 14. In
experiment done by Klein, after he collected passwords of nearly 15000 accounts
that had alphanumerical passwords and he reached the following observation: 25%
of the passwords were guessed using a small yet well-formed dictionary of 3 ×
106 words. Furthermore, 21% of the passwords were guessed in the first week and
368 passwords were guessed within the first 15 min 15.

Single level password
based authentication are not secure enough and are suspected to various attack
such as dictionary attack, brute force attacked and shoulder surfing attack.
Once malicious user logs into account he has full access to all services of
registered user. Currently no cloud service provider has implemented further
security measures with these models to protect services available for
registered user once user has logged in. There is serious issue in sharing scheme.
Security measure applied to protect shared file are not up to the mark. Once
the file is shared with the other user, it sends a link to other user so that
he can access the file but this link is universal.





The Proposed Multilevel Authentication Model for Cloud Computing


The aim of this research is to propose a new scheme
that provides higher security level for cloud services. The proposed scheme is
based on a combination of the concept of multilevel security (MLS) and the
multilevel authentication. The proposed scheme consists of three levels of
security and three level of authentication from lowest to highest. While users
in the lowest level have one password, textual password, the users in the
second level have two passwords, textual and biometrics password. When the
degree of sensitivity of data increased the need for protection is becoming
more crucial. In this scheme the important data exists at the third level with
three passwords for users to login and retrieve their data as described in Figure




















Figure 2. The Proposed Scheme based on Multilevel of


In the proposed scheme multilevel security means
locating the data at different levels of secrecy, the data may exist in one
institution but it varies in the degree of confidentiality and its importance.
The multilevel security hierarchy in the proposed scheme has three levels of
increasing sensitivity. These levels, from lowest to highest, are confidential
(C), secret (S) and top secret (TS) as shown in Figure 3. Users who need to
access data should have the appropriate security access correspond to the
classification level.




Cloud computing provides various internet-based, on
demand services like software, hardware, server, infrastructure and data storage.
To provide privacy services to the intended customer, it is a better option to
use multi-level password generation and authentication technique. Single level
authentication has many problems mainly with sensitive data, as passwords are
easy to break. The proposed scheme provided additional layer of security and
represents a solution for enhancing authentication system based on multilevel


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