International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 5- May 2013
Analization and Comparison of Selective Encryption
Algorithms with Full Encryption for Wireless
Networks
Pavithra. C#1, Vinod. B. Durdi*2
#
M.Tech, Dept. of Telecommunication Engineering, VTU
*Associate Professor, Dept. of Telecommunication Engineering, VTU
Dayananda Sagar College of Engg., Bangalore, Karnataka, India
Abstract— Cryptography has been widely accepted as a
traditional platform of data protection for decades.The most
significant and efficient cryptosystems these days are the
Symmetric key algorithms for cryptography. Hence, they have
a very wide range of applications in many realms. Ad-hoc
networks are the most commonly used type in the present
scenario because of their non-fixed infrastructure. Providing
security to such kinds of network is the main objective of the
work here. In this project, we present a systematic approach
for selective encryption of data. In the present day scenario
where all the wireless ad-hoc network nodes run or work on
battery, Full encryption of all the data may lead to a high
overhead and also waste the computational power or the
resources. Hence, two selective encryption algorithms are
introduced and a secure method for communication between
the user and the entrusted is also being carried out. Eventually,
we carry out an extensive set of experiments using Core Java
and Java cryptosystems. A very attractive GUI is being
designed to make it more user friendly. This can be used
whenever people work remotely and connect to their host
server through VPN. We first create an ad-hoc network and
communicate between the nodes of the network using basic
server client methodology. Two selective encryption algorithms
were developed and more than 50 percent encryption of the
data was maintained in both the algorithms. However, the
security aspect can be changed depending on the kind of the
data which is being communicated.
Keywords— Wireless and Network Security, Data
Confidentiality,
Selective
Cryptographic
Algorithm,
Symmetric Key Encryption, Wireless Networks.
I. INTRODUCTION
A fundamental method of data protection in the area of
information and network security is cryptography, which
has been widely accepted as a traditional platform of data
protection for decades. The application of cryptography is
particularly prevalent in nowadays’ information technology
era, and typical examples include the use of cryptographic
techniques to homeland security, military communications,
financial transactions, and so on [2]. Through the data
encryption and decryption, the protection of data
confidentiality and integrity are achieved. However, based
on the features of wireless devices, a wireless network has
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special security and efficiency requirements
conventional cryptographic algorithms.
for
At present, there are a variety of methodologies to provide
protection for data confidentiality and integrity. As one of
mainstream cryptographic methods, symmetric key
algorithms are widely used due to its efficiency and its
capability of data protection. Typically, a symmetric key
cryptosystem employs a secret key for both encryption and
decryption purposes. This secret key is only shared by the
sender and receiver of the communicating parties and kept
confidential to other irrelevant entities. The secrecy of the
message will be protected well, when the secret key is kept
confidential and distributed securely. Figure 1 illustrates the
schematic diagram of symmetric key encryption and
decryption procedure.
Figure 1: An example of encryption and decryption
processes
For a wireless and mobile network, since wireless devices
are usually equipped with batteries as their power supply,
they have limited computational capability and the issue of
energy saving is one of the most important concerns. As a
result, an efficient selective encryption algorithm is a
potential solution to save considerable power for wireless
devices, and at the same time, to provide sufficient
protection for data communication.
In this paper, we study the issue of selective encryption for
wireless and mobile networks. First, we discuss the
characteristics of wireless ad-hoc networks and the
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necessity of selective encryption. Then we present a
probabilistic selective encryption algorithm based on
various security strategies, which encrypts the transmitted
packets by via of probabilistic function and stochastically
selective algorithm. Through applying the selective and
probabilistic methods, our proposed scheme enhances the
reliability of selective algorithms, and avoids the relevance
between different messages encrypted by symmetric keys.
Thus, it effectively prevents data disclosure to
untrustworthy nodes and economizes the overhead spent on
the data protection for a network. Such a probabilistic
solution is suitable to dynamic and open environments.
be encrypted. If the image consists the picture of a human,
the face part can be recognized using the face recognition
algorithm and only that part of the image can be made to
encrypt. If the image consists some text, only the important
or the key words can be made to encrypt. Lian et al. [6]
worked on an encryption scheme for Advanced Video
Coding (AVC) codec. This algorithm suggests, only those
sensitive data are chosen to be encrypted, such as residue
data and motion vector. Some researchers worked on the
blind signature concept by using hyper elliptical curves
encryption, where the trusted signer can verify the blind
signature without even having any idea about the message.
The rest of this paper is organized in the following way: In
Section II, we review the related work of data protection
methods and selective encryption schemes. Section III
discusses the necessity of selective encryption and states its
challenges. Section IV proposes the selective and
probabilistic solution to encrypt the messages in a wireless
network. We analyse the selective encryption algorithms in
Section V, and finally we conclude in Section VI.
III. THE ISSUES OF SELECTIVE ENCRYPTION
AGLORITHMS
II. RELATED WORK
Recent research has been extensively carried on the area of
cryptography and data encryption [9]. For providing the
data security, a variety of cryptographic techniques are
developed such as symmetric key, asymmetric key or the
digital signature concept. For example, Thamrin et al. [7]
study the issue of random number generation used for
generating pseudo random number in a cryptosystem.
According to the properties of public key-based certificate,
a user S will use the public key issued by an authority and
hash function to register with the authority [1].
Prakash and Uthariaraj [12] present an n-way cryptosystem
for multicast, which uses a hierarchical structure to manage
the nodes in a network, and symmetric keys are used to
achieve the design of multi-crypt.So many key
management functions have been developed such as
rekeying or key revocation have been developed to reduce
the overhead of key exchange. Yonglin Ren, Azzedine
Boukerche, Lynda Mokdad [1] presents the principle of
selective encryption with a propose of probabilistically
selective encryption algorithm. They mainly concentrate on
the symmetric key encryption. By making use of
probabilistic methodology and stochastic algorithm, in the
message encryption process they include proper uncertainty.
Here, the decryption process can be done only by the
authorized person.
Priyanka Agrawal, Manisha Rajpoot [11], Selective
encryption is one of the most promising solutions to reduce
the cost of data protection in wireless and mobile network.
Currently the selective encryption technique is basically
used mainly for multimedia data, as the overhead for
encrypting the multimedia data is very high. The cost for
encrypting or decrypting each multimedia packet is also
very high. In Images only the selected part of the image can
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As we stated above, selective encryption are widely
accepted in energy-aware contexts, due to the fact that they
can
reduce
the
overhead
spent
on
data
encryption/decryption, and improve the efficiency of the
network. In this section, we present the principle of
selective encryption and then study one of the most
important methodologies.
A. The Theory of Selective Encryption
The purpose of selective encryption algorithms is to just
encrypt a certain portions of the messages with less
overhead consumption, but simultaneously, sufficient
messages are encrypted to provide reliable safety to secure
the transmitted message confidentiality [3]. Through
selective encryption, not all messages are necessary to be
encrypted while the entire data transmission can be viewed
to be secure on the whole. Selective encryption is able to
improve the scalability of data transmission and reduces the
processing time.
In the theory of selective encryption algorithms, uncertainty
is involved in the message encryption process to determine
the uncertain pattern of encrypted messages. Here,
uncertainty can enhance the security of data transmission, as
all messages are assumed to own equal importance. Thus,
uncertainty becomes one of the paramount factors when
designing a selective-based cryptosystem. Usually, the more
uncertainty is involved, the more effective the cryptosystem
is. Nevertheless, we also note that an efficient algorithm
will reduce the complexity of selective encryption. Figure 2
is a schematic diagram of a selective encryption process.
Nowadays, selective encryption algorithms are primarily
applied in the realms of energy-aware environments or
large-scale data transmission, such as, multimedia
communications, mobile ad hoc networks (MANETs),
wireless sensor networks (WSNs), etc. For multimedia
communications, it often requires real-time data
transmission, so tremendous audio and video data need to be
transferred securely. Given that all multimedia data are
encrypted, this will consume a great deal of overhead, so
that multimedia data is difficult to transmit timely and the
quality of communication cannot be guaranteed. As such, in
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 5- May 2013
a Wireless Networks, each device uses battery as its power
supply and thereby has constrained computational ability, so
a sensor cannot spend too much computational cost on data
encryption and decryption. Under such circumstances, the
design of a selective encryption algorithm with less
processing time but with relatively high security level is
extremely significant.
both of symmetric key and asymmetric key. Specifically,
our proposed algorithm aims to involve sufficient
uncertainty into the encryption process, while providing
satisfactory security protection to communicating nodes. In
the ad hoc network we discuss, the links between wireless
nodes are always bidirectional and every wireless node has
enough computational power to finish these operations.
A. Secure Key Distribution
Sender
Receiver
Figure 2: The schematic diagram of selective encryption.
B. Probabilistic Encryption
With the definition of selective encryption, we first realize
during the data communication process, it is not necessary
to encrypt all messages. When the communicating data is
scalable or a network is aware of its limited computational
resource, it is not really needed to provide full security
protection on all exchanged information. On the other hand,
we do not wish that eavesdroppers are able to reconstruct
the contents even if they can intercept partial or full
transmitted messages.
As a major selective encryption methodology, the
probabilistic method provides sufficient uncertainty to a
selective-based cryptosystem. In order to adapt the
scalability and to improve the processing capability of a
cryptosystem, the cryptosystem just partially encrypts the
transmitted messages that it wants to protect based on a
certain probability. In the meantime, probability is involved
in the procedure of selective encryption, so that those
selected messages are encrypted in a deterministically
random way. By means of the inclusion of probability,
nobody will exactly know which messages are encrypted
except the communicating parties. Thus, even if there are
malicious attackers which are able to intercept the
communicating messages, they still cannot fully obtain the
selectively encrypted messages or reconstruct all messages.
Consequently, the probabilistic method is widely employed
to enhance the confidentiality of the communications.
IV. OUR PROPOSED SELECTIVE ENCRYPTION
ALGORITHM
In this section, we will present the design of a probabilistic
selective encryption algorithm step by step, which not only
reflects the idea of probabilistic encryption, but also uses
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In order to protect the confidentiality of communicated
messages, our proposed selective encryption algorithm takes
advantage of major categories of cryptographic techniques,
symmetric and asymmetric key algorithms, to guarantee the
security of exchanged information. Nevertheless, due to the
constrained computational power of wireless devices, it is
not realistic to encrypt all information always using the
public key algorithms (PKI). Hence, all official data
communication between two nodes will be encrypted
through symmetric key, and in the meantime, these
symmetric keys will be distributed by public key encryption
algorithm.
In a network, when a node wants to communicate with
another node, a secret key (symmetric key) will be
generated for their communication. Let us denote the
initiating node as S and receiving node as R. If an initiating
node S moves into the neighbourhood of node R, it will
inform the node R of its public key for the authentication
between them. The receiving node R then assigns a secret
key to the initiating node S for the purpose of
encryption/decryption. In order to distribute the secret key
securely, R will encrypt this secret key using the public key
of node S before sending it. Furthermore, R generates
different secret keys for different initiating nodes. Thus,
each sender has a unique secret key for communicating with
the receiver and all information is encrypted using the
corresponding secret key.
Request: {req| IDs, PKs}
Sender
Receiver
Reply: {rep| PKs [SKs]}
Figure 3: The schematic diagram of key distribution.
The figure 3 illustrates the procedure of secret key
distribution between a pair of nodes. The message’s sender
composes a communicating request message req which
contains not only its identifier IDs, but also its public key
PKs, for the purpose of their later mutual authentication.
Once the receiver gets such a communication request, a
secret key (symmetric key) SKs will be generated by the
receiver and encrypted using the public key PKs of the
requester, which is included in the communicating request
message. Later, the receiver composes a communicating
reply rep message and replies it to the communicating
sender, in order to indicate that their communication has
been successfully established. After the sender obtains the
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response from the receiver, it will use its corresponding
private key PRs to decrypt the secret key SKs issued from
the receiver.
B. A Toss-A-Coin Selective Encryption Algorithm
First of all, in order to provide sufficient security to data
encryption, in the first proposed approach, we choose a
relatively high proportion as encryption ratio. Since the
toss-a coin algorithm is a basic approach, little uncertainty is
involved. For all transmitted messages, we divide them to
two groups: the odd number messages and the even number
messages. For instance, messages M1, M3, M5, .… M(2n-1)
represent the odd number messages; messages; M2, M4,
M6, … M(2n) represent the even number messages. When
the sender needs to decide which group should be
encrypted, it makes use of a toss-a-coin method to
determine whether the even number messages or odd
number messages are encrypted. Figure 4 shows the flow
chart of toss-a-coin algorithm.
Toss-A-Coin Algorithm
Start
Divide the array lists into
even and odd nos.
Toss-a-coin
Algorithm
No
If Head
Yes
Encrypt even
Encrypt odd
nos. using
nos using
Combine even and odd ones in
sequence
Send
Figure 4: Flow chart of Toss-a-Coin Algorithm
As an example, we consider the following scenario, in
which the even number messages are encrypted. After the
method of toss-a-coin is applied, the sender makes the
decision that only the even number messages M2, M4 … M
(2n) are encrypted. Thus, half of the whole messages are
chosen to be encrypted and this approach shows a basic
selective encryption algorithm with a semi-determined
encryption pattern. As we described before, the more data
are encrypted, the more secure the communication is, but
the more overhead is spent. Hence, the value of encryption
ratio here is tentatively determined to be 0.5, which means
that 50 percent of the communicated data will be encrypted.
C. A Probabilistic Selective Encryption Algorithm
As the uncertainty in the selective encryption algorithm
increases the security of the data which is being sent also
increases. This algorithm mainly focuses on increasing the
uncertainty in the encryption algorithm. Like in the toss-acoin Algorithm the whole data is divided into a number of
messages M1, M2, M3…. Mn.
Before the communication of the data, the secret key is to be
exchanged. Here we use the standard DES encryption
algorithm for encrypting the data. Each message may
consist of two three or four characters depending on the type
of data. Two random numbers (R1 & R2) are being
generated. The value of the random number is kept more
than the security requirement (SR). Example: if there are ten
messages and the security requirement for the data is 40 per
cent then the random number generated can vary from four
to ten. The messages are being divided into even and odd
like in Toss-a-coin Algorithm. The random number R1
generated is the number of even messages to be encrypted.
The random number R2 generated is the number of old
message to be encrypted. To increase the uncertainty, we
encrypt the even messages from the beginning of the data
and the odd messages from the end of the data. This
increases the uncertainty and hence the security of the data.
Now, the receiver node cannot decrypt the data with only
the DES secret key. It also needs the random numbers
which are being generated to know which messages in the
data are to be decrypted. So the random numbers R1 and R2
are also being encrypted with the same DES secret key and
are sent to the receiver node. The receiver node first
decrypts the random numbers and then decrypts the actual
data. The encryption ratio in this algorithm is not fixed. The
encryption ratio varies with the security requirement. A
highly confidential data can have a high security
requirement. The value of the random numbers being
generated increases with the increase in the security
requirement. Figure 5 shows the flow chart of probabilistic
selective encryption algorithm.
We can see that more uncertainty is included to the
probabilistic encryption algorithm, in comparison to the
toss-a-coin approach, since the encryption ratio is randomly
decided and the encryption pattern is not pre-determined.
Probabilistic Selective Encryption
Algorithm
Start
Divide the array lists into
even and odd nos.
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Encrypt RN1 even
nos. from the
beginning of the text
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Encrypt RN2 odd
nos. from the end
of the text
International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 5- May 2013
selective encryption. Hence, selective encryption is more
efficient and is able to better utilize the computational
resource of a wireless device.
Because probabilistic encryption does not fix the encryption
probability, the encryption proportion fluctuates in a
relatively larger range. Thus, probabilistic encryption owns
more uncertainty than toss-a-coin encryption. Also we
compare these two selective encryption algorithms with full
encryption.
Generate 2 random nos(RN).,
1 for even; 1 for odd
Figures 6, 7 and 8 show the graphs for encryption and
decryption of the two selective encryption algorithms
discussed and the full encryption. The graph is plotted for
the time in ms vs. no. of data strings (characters), the text is
divided into.
Send
Figure 5: Flow chart of Probabilistic Selective Encryption
Algorithm
D. The Exchange of Selective Pattern
Once the sender of the communicating parties transfers the
official traffic by means of selective encryption, it will let
the corresponding receiver know the encryption pattern of
the exchanged messages in a secure way. First, the sender
will summarize the pattern based on those selectively
encrypted messages and indicate which messages have been
encrypted. Subsequently, it composes the encryption pattern
in a pattern related message and then sends it to the
messages’ receiver. In order to securely distribute this
pattern message, the public key of the receiver is also used
to encrypt this pattern-related message. Thus, the receiver
can use its corresponding private key to decrypt the pattern
message and thereby keep track of the information of
encrypted messages. Through such a public key based
method, the process of pattern information exchange is kept
confidential only to the communicating parties.
Figure 6: Time vs no of data strings in toss-a-coin algorithm
Figure 7: Time vs no of data strings in probabilistic
selective encryption algorithm
V. RESULTS
In this section, in order to study our proposed probabilistic
selective encryption scheme and observe its characteristics,
we carried out a set of experiments within Java. The
standard DES algorithm is employed for communication
between a pair of nodes and the secret keys have a length of
64 bits. This is determined by the computational capability
and characteristics of wireless nodes in the wireless
network.
Figures 9 and 10 show comparison of the ‘Toss-a-coin’,
‘Probabilistic’ and ‘Full’ with the time taken vs. number of
data strings for encryption and decryption respectively.
As we stated before, we analyse two different selective
encryption algorithms, “toss-a-coin” and “probabilistic”.
We can learn that both toss-a-coin and probabilistic have an
obvious lower encryption time which is caused due to the
fact that selective encryption takes an effect and the
overhead is greatly saved and the data transmission can be
speeded up by virtue of toss-a-coin and probabilistic
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 5- May 2013
out and only that part of the image or video can be
encrypted.
REFERENCES
Figure 8: Time vs no of data strings in full encryption
Figure 9: Time taken vs. no. of data strings for Encryption
Figure 10: Time taken vs. no. of data strings for Decryption
VI. CONCLUSION AND FUTURE WORK
Selective encryption is one of the most promising solutions
to reduce the cost of data protection in wireless and mobile
networks. In this paper, we have presented a novel solution
for selective encryption to achieve data protection
effectively while with reasonable costs. These algorithms
were found very effective and maintain security and also
reduce the overhead. The analysis of the two selective
algorithms were made and the compared with the full
encryption method. The results obtained show that the time
spent on these algorithms is very less than the full
encryption method.
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The selective encryption algorithms developed can be
extended to multimedia messages. The multimedia
messages require a very high overhead in wireless networks.
The sensitive part of the images or the videos can be found
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