Improving Cloud Security Using Multi Level Encryption and Authentication

International Journal of Innovative Research in Information Security (IJIRIS) ISSN: 2349-7017(O)
Issue 8, Volume 2 (August 2015) ISSN: 2349-7009(P)
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© 2014-15, IJIRIS- All Rights Reserved Page -01
Improving Cloud Security Using Multi Level
Encryption and Authentication
A.Prakash*
M.Satish T.Sri Sai Bhargav Munesswari.G
III year Student III year Student III year Student Associate Professor
Department Of Information Department Of Information Department Of Information Department Of Information
Technology Technology Technology Technology
SSN College of Engineering SSN College of Engineering SSN College of Engineering SSN College of Engineering
Abstract— As people have become more social and electronically attached, the concern for information sharing over
the internet still persist. As known many powerful cryptographical approaches have been proposed in the past which
are practically impossible to break, yet there exists a major concern of total encryption and decryption time taken as a
whole. It is a known fact that in encrypting a large chunk of data, traditional asymmetric key algorithm may be
slower to symmetric key algorithm by 1000 times or more. Hence this paper proposes a hierarchical structure in which
the parties are first authenticated, then exchange keys by asymmetric key algorithm, then do actual encryption and
decryption by the symmetric key algorithm. This will be useful to improve the security in cloud applications.
Keywords— Modified Rivest Shamir Adleman Algorithm (MRSA); Modified Triple Data Encryption Standards
(M3-DES); Diffie-Hellman Key exchange Algorithm (D-H Algorithm).
I. INTRODUCTION
In Cloud Computing the data is transferred over the internet. Even many classified and important transactions occur
over the internet and hence it is important to have some security i.e. some encryption standards to protect the data which
is transmitted over the channel. With the increasing numbers of people who are involved in the intrusion side, it is
necessary to have a strong approach to security so that all attacks and factors to attack are met and hence avoided.
Generally the following approach is applied wherein the user at one end encrypts the data into cipher text and then sends
over the channel and the receiver receives the cipher text and then reverts it back to the original data by decryption. So
here the intruder sitting in the middle gets only the cipher text and without the knowledge of the key he could not revert it
back to the original text, hence this approach is applied which is also called as cryptography.
Fig 1. Basic Cryptography with Man-In-The-Middle
Hence the Fig.1 gives a brief idea about the Cryptography.
Tracing the history of cryptographic algorithms we ended up finding many algorithms. Every Algorithm we found had
their own pros and cons. These algorithms are broadly classified as
1. Symmetric/Private Key Algorithms
2. Asymmetric/Public Key Algorithms
The Symmetric key Algorithm uses only one key for encryption and decryption of data. Whereas the Asymmetric key
Algorithms uses two keys private and public keys .Public key is used for encryption and private key is used for
decryption (e.g. RSA). The list of Symmetric Key Algorithms is as follows:
1. Data Encryption Standards(DES)
2. Triple Data Encryption Standards(3-DES)
3. Advanced Encryption Standards(AES)
The list of Asymmetric Key Algorithms is as follows:
1. Rivest Shamir Adleman Algorithm (RSA)
2. Diffie-Hellman Algorithm
There are many such algorithm available, the above are the most popular and most used one’s. The main disadvantage of
the above algorithms is,

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1. DES- Already cracked and the cryptanalysis tool is made available.
2. 3-DES- Very difficult to break, but due to the problem of weak keys at time very rarely can be easily broken.
3. RSA- This is a good algorithm but runs slower to the other private key algorithms due to its exponential raising.
II. LITERATURE SURVEY
In [1], Secured Multiparty computation is been discussed which is a technique that analyses the private data and
results are computed by the parties having similar background on minimising the threat of disclosure. In [3],a secured
sum is being developed which allows the parties to work on their inputs devoid of sharing with others which is highly
secured. On top of secured sum an algorithm was developed to share the simple integer information at all iterations on
anonymous id assignment. In [5], we use a secured computation function in which the parties need not disclose their
integer information to each other. This function being developed is popular in data mining applications. In [6] id's are
generated randomly with no central authority in a network fashion. In [7] we use Anonymous ID Assignment (AIDA)
technique which is a sharing algorithm and requires unbounded number of iterations. Dr. James H. Yu [8] in this
concluded that many networks are prone to attack and generally people ignore it. As network security increases system
performance decreases. J. Daemen [10] concluded that AES is faster and more efficient than other encryption algorithms.
Kyung Jun Choi et.al [11] investigated the algorithms suitable for wireless networks and found that MD5 and RC4 stand
above all encryption algorithm. Here we have been going through many encryption algorithms including AES, DES,
3DES, RC2, Blowfish, and RC6 and their commonality and performance related aspects is also been spoken of. The
results show that AES is faster and more efficient than other encryption algorithms. When the transmission of data as a
criteria is taken there is insignificant difference in performance related aspects of different symmetric key schemes.
A study in [16] is been performed on various secret key algorithms like DES, 3DES, AES, and Blowfish. Input files of
various size are taken and each of the above algorithm is made to be implemented on the input files and results is been
compared indicating that Blowfish has high performance when compared to other encrypting algorithms. Also AES
stands above 3DES and DES. In addition, the advantage of DES over 3DES is that it has triple throughput.
Ruangchaijatupon et al. [4] shows the energy consumption of different symmetric key encryption algorithms on hand-
held devices. It is found that only after 600 encryption done on a 5 MB file using 3DES the battery power is been
identified as 45% and other encryption algorithm is not so efficient in power consumption as battery dies of rapidly
before even completion of 600 trials. A Crypto++ Library [17] is a free C++ class library containing cryptographic
schemes. It evaluates the performance between the selected algorithms. Thus it concludes that Blowfish and AES have
the better performance than other encryption algorithms .In [16, 18], performance between selected symmetric
encryption algorithm is been presented. In case of packet size Blowfish stands above all algorithms followed by RC6.
Also 3DES has low performance issue when compared to DES. In terms of time consumption RC2 is weak by
consuming more time than the rest of algorithms. Secondly it’s been concluded that AES stands above 3DES, DES and
RC2. These evaluations are made only on Windows OS. Salama et al. [19] On basis of different settings such as size
of blocks, data types used, CPU time and different key size a comparison study is made on encryption algorithms (AES,
DES, and 3DES, RC2, Blowfish, and RC6). The results show that Blowfish and AES is more efficient when
compared to others. Elkilani et al. [18 ]Performance of real time video streaming was taken as a criteria and algorithms
like RC4, AES, XOR is been tested and AES has less time overhead than the two.
III. ARCHITECTURE FOR IMPLEMENTATION IN CLOUD
The following approach has to applied in the cloud computing scenario when a user say the client gives request to
some service which is present in a virtual machine of a cloud so this becomes the server (also the vice versa) see in Fig2.
The Architecture used here has three phases as follows:
 Phase 1:
o Here the User says A wants to connect to Web Service running in Virtual Machine 1 of the Cloud. So
First the user is authenticated for connection establishment the so called Long-Term and Short-Term
Keys are given to the Virtual Machine 1 by the Hypervisor of the respected Virtual Machine from the
Key Schedule. So at the end of Phase1, A is connected to the Web Server.
 Phase 2:
o Now having the connection established, when A wants to gain access of any data say file transfer or
uploading of data or any signs data transfer then Virtual Machine 1 performs the key transfer with A,
connects to its Database which may present in some other VM, Encrypts it using the Algorithm
proposed below and then finally transfer it to A. A at receiving end decrypts the cypher and reads the
data.
 Phase 3:
o So this phase specifically deals with the scenario when the Virtual Machine1 wants to access the data
present in the Virtual Machine say VMx which is in turn present in the other Datacentre of same or
different cloud, So here what happens is the VM1 goes through all the phases discussed above and then
gets connected to VMx .

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Fig2. Architecture for cloud implementing the proposed system
The proposed approach can be also applied in the scenario where the client and server are independent machines.
IV.PROPOSED LAYERED HIERARCHICAL STRUCTURE
In our proposed hierarchical structure there are three algorithms as a whole are used: Diffe-Hellman Key Exchange
algorithm, MRSA algorithm and M3-DES algorithm. The overall architecture diagram of the entire methodology of
security is shown in Fig.3
Fig 3. Multilevel Encryption and Authentication
Procedures of algorithms used:
Diffie-Hellman Key Exchange Algorithm:
1. Consider two parties A and B who agree upon the key transfer and a intruder say C whose intension is to
know the message which is being transferred.
2. A or B send two values say (g and n) to either of them.
3. The intruder C has values g and n.
4. Now A and B produce a random number each say x and y respectively.
5. Now A transmits X= ((g^x) % n) to B and B transmits Y=((g^y) % n) to A.
6. The intruder C has now got hold of value g, n, X, Y given these values the intruder cannot find the value of
x and y because this problem is called Discrete Logarithm Problem (DLP) till today it is considered to be a
computationally in-crackable problem. I.e. it cannot be broken in a given reasonable amount of time .Given
X, g, n it is not computationally feasible to calculate the value of x.

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7. Now A finds KeyA=((Y^x)%n) and B finds KeyB=((X^y)%n).
8. Now both parties agree upon the same key since KeyA==KeyB.
Having this said the D-H algorithm is susceptible to the Man in the middle attack. Wherein the intruder C somehow gets
hold of the router and disconnects A from the network and he himself acts as A. So we need some Authentication by
which we can verify that we talking to the right person, which is given by MRSA.
MRSA Algorithm:
As far as our approach is concerned, It is crucial that authentication process plays a vital role in the actual algorithm
of RSA. Here the public keys of A and B are d1, d2 respectively and the private keys of A and B are e1, e2
1. Parties A and B share with either of them their public key say d1 and d2 respectively.
2. Now A wants to authenticate that the opposite party is B, so what A does is he asks B to encrypt his own private
key say e2 as the message using the key d1 and send it to A.
3. Now A having the encrypted message , decrypts it using his private key e1.Which intern gives him e2
4. A checks that
If (d2⋅e2 == 1 (mod φ(n))
The opposite user is B.
Else
There is some intruder or say man in the middle.
M3-DES Algorithm:
The Algorithm used for Triple DES is the same, but the problem or a possible micro hole in 3-DES which is
Weak, Semi-Weak and Demi-Weak keys is dealt with here in this algorithm.
Weak Keys:
These are keys that cause the encryption mode of DES to act identically to the decryption mode of DES. The
Modified Triple Data Encryption Standard Algorithm is as follows:
1. The Key Scheduler generates a 56-bit for a single block of DES as shown below.
2. The First key say K0 is then passed through the block called Weak Key Detection(WDK) Block
 If the key is not Weak then it is passed for encryption
 Else it is resent to the key scheduler indicating the need for generating the new key.
Weak Key Detection (WDK) Block:
In the block a search for weak key is made shown in fig.4, if the search is found then the key is resent to the key
scheduler indicating the need for generating the new key. The Weak, Semi-Weak and Demi-Weak keys in DES are as
follows:
Weak Keys:
0101010101010101, fefefefefefefefe, 1f1f1f1f1f1f1f1f, e0e0e0e0e0e0e0e0
Semi-Weak:
01fe01fe01fe01fe fe01fe01fe01fe01
1fe01fe01fe01fe0 e01fe01fe01fe01f
01e001e001e001e0 e001e001e001e001
1ffe1ffe1ffe1ffe fe1ffe1ffe1ffe1f
011f011f011f011f 1f011f011f011f01
e0fee0fee0fee0fe fee0fee0fee0fee0
Demi-Weak:
1f1f01010e0e0101 e00101e0f10101f1
011f1f01010e0e01 fe1f01e0fe0e01f1
1f01011f0e01010e fe011fe0fe010ef1
01011f1f01010e0e e01f1fe0f10e0ef1
fe0101fefe0101fe
e0e00101f1f10101 e01f01fef10e01fe
fefe0101fefe0101 e0011ffef1010efe
fee01f01fef10e01 fe1f1ffefe0e0efe

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e0fe1f01f1fe0e01
fee0011ffef1010e 1ffe01e00efe01f1
e0fe011ff1fe010e 01fe1fe001fe0ef1
e0e01f1ff1f10e0e 1fe001fe0ef101fe
fefe1f1ffefe0e0e 01e01ffe01f10efe
fe1fe001fe0ef101 0101e0e00101f1f1
e01ffe01f10efe01 1f1fe0e00e0ef1f1
fe01e01ffe01f10e 1f01fee00e0ef1f1
e001fe1ff101fe0e 011ffee0010efef1
1f01e0fe0e01f1fe
01e0e00101e1e101 011fe0fe010ef1fe
1ffee0010efef001 0101fefe0101fefe
1ffee0010ef1fe01 1f1ffefe0e0efefe
01fefe0101fefe01
1fe0e0f10ef1f10e fefee0e0fefef1f1
01fee01f01fef10e e0fefee0f1fefef1
01e0fe1f01f1fe0e fee0e0fefef1f1fe
1ffefe1f0efefe0e e0e0fefef1f1fefe
Fig 4. DES with Weak Key detection
Proposed Algorithm:
The main purpose of this approach is to reduce the overall time taken for the entire security process as a whole.
The Algorithm is as follows:
1. The Authentication of users is done by the MRSA approach given above.
2. Each of the users is allocated with two pairs of keys
1) Long-term keys:
These keys will be unique and can be there for connection establishment.
2) Short-term keys:
These Keys will be allocated to each user after each conversation between two users. This is done
because while authentication the users will get to know the private keys of each other, and hence it is
not secure to have the same key even after the disconnection.
3. After authentication the users agree upon the key value which will be used for encryption using Diffie-Hellman
key exchange algorithm as discussed above.
Finally the M3-DES is run for encryption and decryption based on the key decided in step 3.
V. EVALUATION RESULTS
To justify our fact as given above that time taken for encryption is 100 to 1000 times more for large data set if we use
asymmetric key algorithms to symmetric key algorithms, we use a simulation tool to run both the symmetric and
asymmetric key algorithms which are Triple DES and RSA respectively.

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Here in our approach we have used MRSA for authentication while for encryption and decryption we have used
Modified Triple Data Encryption Standards. The following is a table which shows the time taken for Encryption for M3-
DES and RSA for packets or data of different size.
Input
Size(KB)
M3-DES RSA
45 51 55
55 45 49
96 77 90
236 114 120
319 155 165
560 170 185
899 300 350
5400 1167 1445
Throughput
(MB/sec)
2.01 1.54
Table1. Time Taken for encryption in milliseconds
The following is a table which shows the time taken for Decryption for M3-DES and RSA for packets or data of different
size in milliseconds.
Input
Size(KB)
M3-DES RSA
45 51 62
55 45 58
96 65 56
236 70 65
319 85 156
560 160 170
899 175 200
5400 830 905
Throughput
(MB/sec)
4.12 2.21
Table2. Time Taken for decryption in milliseconds
The encryption and decryption throughputs are shown in fig.5 and fig.6.
Fig 5. Encryption Throughput

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Fig 6. Decryption Throughput
Hence the results shows that asymmetric key algorithms are very slow when compared to the symmetric key algorithms.
We have used very small data sets but if we use very large data set say of 100 MB file then for encrypting any
asymmetric key algorithm will increase time taken in an exponential order and but when we use symmetric key
algorithms whatever may be the file almost same time is used because the rounds in the M3-DES is just going to permute
the same text and hence the time will not increase in an exponential order. So based on these results we have used M3-
DES rather than using RSA.
VI.CONCLUSIONS
This layered approach gives a total stability to the user, wherein the hosts are first authenticated, exchange keys and
finally encrypt and transfer the cipher text. The receiver receives the cipher, decrypts using the agreed key and reverts or
gets the message without intrusion. We have also shown the results for encryption and decryption throughputs. So, we
argue that this multilevel algorithm improves security in public clouds.
REFERENCES
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Computational Services”, IJRRECS,Volume-1,Issue-6,1006-1011.
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[13] N.Ferguson, D.Whiting, B.Schneier, J. Kelsey, S.Lucks, T .Kohno. "Helix fast encryption and authentication
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