International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
Enhancing the Security of Cloud Computing by Building
Hybrid Cryptography Algorithms
Tahera Begum
Md. Ebrahim Hossain
Lecturer
Dept. of Information & Communication Technology
Moinuddin Adarsha Mohila College
Sylhet-3100, Bangladesh
Assistant Professor
Dept. of Computer Science & Engineering
Leading University
Sylhet-3100, Bangladesh
ABSTRACT
In the present circumstances, the Cloud Computing is very wellknown and flexible technology. It provides massive data centre
to handle the large amount of information. The Cloud
Computing benefits the organizations to handle their large
volume of information. The major issue in cloud computing is
data security, because most of the customers are sharing same
cloud. This study aims at designing a new security method by
using a hybrid cryptosystem, for data security in the cloud. The
necessity for the current investigation is to protect data from
unauthorized access or hackers in cloud at the time of data
transmission by encrypting the user data. Cloud computing
constitutes several security issues including data access control,
identity management, auditing, integrity control and risk
management. So, this hybrid cryptosystem is designed and
comprises of both symmetric and asymmetric cryptography
algorithm in which Blowfish symmetric algorithm deals with
data confidentiality whereas, RSA asymmetric algorithm deals
with an authentication. This method also includes the Secure
Hash Algorithm – 256 (SHA-256) for data integrity. This study
concluded that the proposed method provides high security on
data transmission over the internet and proper network access
on demand to a shared tank of constructive computing
resources, like net, server, and storage application.
It enables the client to constantly monitor the server uptime,
abilities, and allotted network storage.
1.1.1.3 Scalability and rapid elasticity
This cloud characteristic enables cost-effective running of
workloads that require a vast number of servers but only for a
short period.
1.1.1.4 Measured and reporting service
Measuring & reporting service enable both the provider and the
client to monitor and report what services have been used and
for what purpose.
1.1.1.5 Security
Cloud services create a copy of the data that is stored to prevent
any form of data loss. If one server loses the data by any chance,
the copy version is restored from the other server. This feature
comes handy when several users work on a particular file in
real-time and a file suddenly gets corrupted.
1.1.1.6 Large network access
The client can access the cloud data or transfer the data to the
cloud from any place just with a device and internet connection.
1.1.1.7 Economical
Cloud computing, Cryptography, Blowfish, RSA, SHA-256
There is no covered up or additional charge which needs to be
paid. The administration is economical, and often, some space is
allotted for free.
1. INTRODUCTION
1.1.2 Deployment models
1.1 Cloud computing
There are four deployment models in cloud computing. These
are:
Keywords
Now-a-days most people and firms are migrating to cloud
because the cloud is much cheaper and convenient. For some
computer owners, finding enough storage space to hold all the
data they acquired is a real challenge. Some people buy large
quantity of data or larger space hard drives and still faced with
storage space challenges. Most computer owners that are eager
to make space for new information might delete entire folders
worth of old files. With this new technology of cloud computing
people are finding it much easier to buy huge amount of space
on cloud, this Cloud really refers to saving data to an off-site
storage system maintained by a third party. Storing data in a
remote location instead of storing information on our computer's
hard drive or other local storage unit.
1.1.1 Characteristics of cloud computing:
1.1.1.1 Resources pooling
Resource pooling means that a cloud service provider can share
resources among several clients, providing everyone with a
different set of services as per their requirements.
1.1.2.1 Private cloud: Private Cloud is the one in which
cloud infrastructure is established within the organization and
provides limited access to the users. Since, only privileged users
can access the resources on the cloud, it is considered as most
secure of all other deployment models. It is deployed where the
number of users accessing the information is small.
1.1.2.2 Public cloud: Public Cloud is the one in which
cloud infrastructure is shared among different organizations.
The public cloud is managed by some third party who lease out
the resources to the organizations as per their demand. Hence,
the public cloud supports the feature pay-as-you-go pricing.
Public clouds are vulnerable to data tampering as there are
multiple organizations accessing the applications on sharing
basis and hence, it may give easy access to some intruder.
1.1.2.3 Hybrid cloud: Hybrid Cloud is the combination of
different clouds. As it is the combination of models, it offers the
advantages of multiple deployment models. It provides ability to
1.1.1.2 On-demand self-service
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
maintain the cloud as recovery of data is easy in this cloud. It
provides more flexibility.
1.1.2.4 Community cloud: Community Cloud is the one in
which the cloud infrastructure is shared between different
organizations with same interests or concerns. The
organizations having same requirements (like security, policy,
etc.) agree to share the resources from the same party or cloud
vendor. Hence, community cloud is basically a public cloud
with enhanced security and privacy just like that in private
cloud. The infrastructure may be maintained within the
organization or outside the organization.
ordinary plain text into unintelligible text and vice versa. It is a
method of data storage and transmission in a particular form so
that only those for whom it is intended can read and process it.
Cryptographic algorithms are the study of techniques for
ensuring the secrecy and/or authenticity of information.
Cryptography classified as Symmetric cryptography and
Asymmetric cryptography techniques.
1.2.1 Characteristics of cryptography:
1.2.1.1 Confidentiality
Information can only be accessed by the person for whom it is
intended and no other person except him can access it.
1.2.1.2 Integrity
Information cannot be modified in storage or transition between
sender and intended receiver without any addition to
information being detected.
1.2.1.3 Non-repudiation
The creator/sender of information cannot deny his or her
intention to send information at later stage.
1.2.1.4 Authentication
The identities of sender and receiver are confirmed. As well as
destination/origin of information is confirmed.
1.2.2 Types of cryptography
Fig 1: Cloud computing deployment models
1.1.3 Service models
Cloud computing generally provides three services, namely,
Software as a Service (SaaS), Platform as a Service (PaaS), and
Infrastructure-as-a-Service (IaaS).
1.1.3.1 Software as a Service (SaaS): SaaS permits
people to use cloud-based web application. Email services such
as Hotmail and Gmail are the example of Software as a Service
(SaaS).
1.1.3.2 Platform as a Service (PaaS): PaaS denotes
cloud platforms that provide runtime environments for
developing, testing, and managing applications, examples of
PaaS would include Heroku and Google App Engine.
1.1.3.3 Infrastructure-as-a-Service (IaaS): IaaS is a
cloud facility and service that offers basic computing storage,
infrastructure, servers and networking resources. To paraphrase
this, IaaS is a virtual data centre wherein major IaaS providers
include Amazon Web Services, Microsoft Azure and Google
Compute Engine.
Cryptography can be divided into following three categories
depending upon the types of key used: secret key (symmetric)
cryptography, public key (asymmetric) cryptography and hash
functions.
1.2.2.1 Symmetric cryptography
Symmetric encryption transforms plaintext into cipher-text
using a secret key and an encryption algorithm. Using the same
key and a decryption algorithm, the plaintext is recovered from
the cipher-text. The various algorithms for symmetric key
cryptography are not limited to (AES, DES, and Blowfish).
1.2.2.2 Asymmetric cryptography
Asymmetric key encryption or public key cryptography uses
different keys to encrypt and decrypt information. In this
methodology, each of the participants of the communication has
two keys; one is public key which is shared with all the
participants, and the other is private key which is secret and
only the intended receiver knows it. Though the public and
private keys are apparently different, these are mathematically
related.
Each
of
the
public
key
has
a corresponding private key. This technique can provide
integrity, authentication, and non-repudiation. A few standard
Asymmetric Key Algorithms are ElGamal, ECC, RSA, DSA,
Diffie-Hellman.
1.2.2.3 Hash functions
Fig 2: Cloud computing service models
1.2 Cryptography
Cryptography which plays an important role in terms of
information security and protection of information.
Cryptography is concerned with the process of converting
Hash functions are termed one-way encryption other than the
message digests. To ensure it inconceivable for the details or
length of the plaintext to recapture hash values computed on the
basis of plaintext rather than fixed length. To encode passwords
a lot of OS frequently employ hash function. In addition, it
gives a mechanism to confirm software integrity checking it
used to defend the file from not been adjusted by virus or
hacker. To give a digital fingerprint of a file's contents hash
methods are frequently adopt.
SHA-1, SHA-2, SHA-3, MD4 and MD5 are some of the regular
Hash key algorithms.
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
Fig 3: Types of Cryptography and Various Cryptographic Algorithms
2. LITERATURE REVIEW
1) Jain and Agrawal have proposed a hybrid cryptography
algorithm using a combination of two symmetric cryptographic
techniques, Data Encryption Standard (DES) and International
Data Encryption Algorithm (IDEA) to strengthen the encryption
algorithm. Authors are mainly concerned about the security of
sensitive data transfer over different networks for example
Military data and Banking transactions etc.
2) Sunita Rani and Ambrish Gangal ―Cloud Security with
Encryption using Hybrid Algorithm and Secured Endpoints‖
proposed a hybrid algorithm for securing the user data initially
the message will be encrypted with the Ceaser cipher and the
result will be encrypted with the RSA algorithm and result will
be again encrypted with mono alphabetic substation method.
3) Ali defined a hybrid encryption algorithm using Advanced
Encryption Standard (AES) and Blowfish encryption algorithm
for specific application like in bank, military, big websites those
handle big data base, and in network companies etc. Author also
examined different encryption algorithms like Advanced
Encryption Standard (AES), Data Encryption Standard (DES),
Blowfish Encryption algorithm and Rivest Shamir Adleman
(RSA) Encryption algorithm with the help of Statistical Tests.
4) Jasleen Kaur and Dr. Sushil Garg, ―Security in Cloud
Computing using Hybrid of Algorithms‖ in the proposed work
blending with Digital Signature with RSA algorithm and
Blowfish algorithm. Initially a hash is framed to create message
digest, for sign the document RSA private key algorithm was
used for encryption and for verifying the document Blowfish
algorithm was used.
5) Najar and Dar, have proposed efficient, tough and secure
hybrid encryption algorithm design with the help of Symmetric
key algorithm like Advanced Encryption Standard (AES) and
Asymmetric key algorithm like Rivest Shamir Adleman (RSA)
algorithm which is responsible for management of key, and
Secure Hash Algorithm-1 (SHA-1) used for digital signature.
3. SYSTEM MODEL
3.1 Methodology
This new hybrid cryptography method includes the combination
of both symmetric and asymmetric algorithm for more excellent
result. Each cryptography method follows the encryption and
decryption process. In encryption process the original data is
transformed into cipher data, which is not understand by any
human or person. To get the original data from cipher data
decryption process is used. In this study two time encryption
and decryption process is performed because the use of
symmetric and asymmetric algorithm.
Before encryption and decryption, RSA, Blowfish and SHA-256
are discussed here.
3.1.1 RSA
RSA is an asymmetric cryptographic technique that uses private
key and public key. Messages are encrypted by using the public
key of specific receiver and decryption is done by using the
private key of receiver. The RSA algorithm is named after those
who invented it in 1978: Ron Rivest, Adi Shamir, and Leonard
Adleman.
3.1.1.1 Features of RSA:
Public/private key generation.
Encrypt with either public or private key.
Decrypt with matching public or private key.
Create digital signatures.
Verify digital signatures.
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
Supports key sizes ranging from 512 bits to 4096 bits.
Supports hash algorithms: MD5, SHA-1, SHA-2
(SHA-256, SHA-384, SHA-512), and more.
Thread safe.
The steps involved in the process are:
1. Choose two distinct large prime numbers, p and q.
2. Calculate n = p*q.
3. Calculate ϕ(n) = (p-1)*(q-1).
4. Select an integer e such that 1<e<ϕ(n) and gcd(e,
ϕ(n)) =1; that is, e and ϕ(n) are co-prime.
5. Calculate d such that e*d = 1 mod ϕ(n).
n is known as the modulus for public and private keys.
e is known as the public exponent or encryption
exponent or just the exponent.
d is known as the secret exponent or decryption
exponent.
The pair (e, n) forms public key and the pair (d, n) forms private
key. To compute cipher text (C) of message (M) uses the
following equation
C M e mod (n
(1)
To decrypt the cipher text (C), use the following equation.
P C d mod (n
(2)
• Simple: Blowfish uses only primitive operations such as
addition, XOR and table lookup making its design and
manipulation simple
• Secure: Blowfish has a variable key length up to a maximum
of 448 long, making it both flexible and secure.
3.1.2.2 Basic operations:
1. Sub key Generation:
•
•
•
•
•
Key Size is variable but blowfish algorithm generates
very large sub-keys. The key size is in the range of 32
bits to 448 bits or 14 words.
Concept of P-array consists of 18, 32 bit sub-keys
There are 4 S-boxes containing 256 entries of 32 bits
P-array is initialized first then four s boxes with fixed
string
Then P-arrays are XORed with sub keys from P1 to
P18. Once the sub keys are generated the encryption
process begins.
2. Data encryption and decryption:
This process involves the iteration of a simple function
16 times. Each round contains a key-dependent permutation and
key and data substitution.
•
Blowfish is a very fast algorithm which takes 64 bit
input as plaintext and generates 64 bit output cipher
text.
•
It uses the concept of P-array which uses 32 bit sub
keys and there are 18 P-arrays P1 to P18
•
Blowfish Algorithm runs 16 times i.e. 16 rounds
A graphical representation of the Blowfish algorithm appears in
Figure-5. This structure is known as Fiestal network. Graphical
representation of F appears in Figure-6. The function divides a
32-bit input into four bytes and uses those as indices into an Sarray. The lookup results are then added and XORed together to
produce the output. Because Blowfish is a symmetric algorithm,
the same procedure is used for decryption as well as encryption.
The only difference is that the input to the encryption is
plaintext; for decryption, the input is cipher text.
Fig 4: Block diagram of RSA algorithm
3.1.1.2 Advantages of RSA algorithm:
• RSA is stronger than any other symmetric key algorithm.
• RSA has overcome the weakness of symmetric algorithm i.e.
authenticity and confidentiality.
3.1.1.3 Disadvantages of RSA algorithm:
1. RSA has too much computation.
3.1.2 Blowfish
Blowfish is a symmetric encryption algorithm, that it uses the
same secret key to both encrypt and decrypt messages. Blowfish
is also a block cipher that it divides a message up into fixed
length blocks during encryption and decryption. The block
length for Blowfish is 64 bits; messages that aren't a multiple of
eight bytes in size must be padded. It was designed and
developed by Bruce Schneier in 1993.
3.1.2.1 Features of Blowfish:
• Fast: Blowfish encryption state on 32 bit microprocessors.
• Compact: Blowfish can execute in less than 5KB memory
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
Fig 5: Graphical representation of Blowfish algorithm
P is an array of eighteen 32-bit integers. S is a two-dimensional
array of 32-bit integer of dimension 4x256. Both arrays are
initialized with constants, which happen to be the hexadecimal
digits of π (a pretty decent random number source). The P-array
and S-array values used by Blowfish are pre-computed based on
the user’s key.
a message digest function with a block size of 512- bit generates
256-bit message digest.
A message is processed by blocks of 512 = 16 × 32 bits, each
block requiring 64 rounds.
3.1.3.1 Basic operations:
• Boolean operations AND, XOR and OR, denoted by
˄,
and ˅ respectively.
• Bitwise complement, denoted by ¯.
• Integer addition modulo 232, denoted by A + B.
Each of them operates on 32-bit words. For the last
operation, binary words are
interpreted as integers written in base 2.
• RotR(A, n) denotes the circular right shift of n bits of
the binary word A.
• ShR(A, n) denotes the right shift of n bits of the binary
word A.
• A || B denotes the concatenation of the binary words A
and B.
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic
hash functions designed by the United States National Security
Agency (NSA) and first published in 2001. It has several
variants, all of which use the same algorithm but use different
constants.
Fig 6: Graphical representation of Function module (F)
In effect, the user’s key is transformed into the P-array and Sarray. This process is known as sub-key generation. The key
itself may be discarded after the transformation. The P-array
and S-array need not be recomputed as long as the key doesn’t
change, but must remain secret.
The SHA-2 family of hash functions includes:
SHA-224
SHA-384
SHA-256
SHA-512
SHA-512/224
SHA-512/256
3.1.2.3 Advantages of Blowfish algorithm:
Faster than other encryption algorithms, such as the
Data Encryption Standard (DES).
Blowfish is unpatented and free to use. This means
anyone can take and use Blowfish for whatever they
want to.
The Blowfish algorithm also has a lesser amount of
operations to complete compared to other encryption
algorithms.
The key schedule of Blowfish takes a long time, but
this can be advantageous, as brute force attacks are
more difficult.
S.
No
Comparison
Parameters
MD-5
SHA
1
Security
Less Secure
High Secure
2
Message Digest
Length
128 bits
160 bits
3
The key schedule of Blowfish takes a long time,
equivalent to encrypting 4KBs of data, which can be a
disadvantage or an advantage. On the Disadvantage
side, it takes a very long time to do.
The small block size of Blowfish means that Birthday
Attacks can occur and compromise the encryption
algorithm.
It is followed by Twofish, which was created to
Attack required to
find out original
message
2128 bit
operation
2160 bit
operation
4
Attacks to try and
find two messages
producing the same
MD
264 bit
operation
280 bit
operation
replace Blowfish, as it is better in most ways.
5
Speed
Faster, only
64
iteration
Slower,
required
80 iteration
3.1.2.4 Disadvantages of Blowfish algorithm:
Table 1. Comparison between MD-5 and SHA
3.1.3 SHA-256
SHA-256 (secure hash algorithm) is a cryptographic hash
function with digest length of 256 bits. It is a keyless hash
function. The SHA-256 algorithm is one flavor of SHA-2
(Secure Hash Algorithm 2), which was created by the National
Security Agency in 2001 as a successor to SHA-1. SHA-256 is
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
Table 2. Comparison of SHA Functions
S.
No
Algorithm
and
Variant
1
Output size
160 bits
2
Internal
state size
160 bits
3
Block size
512 bits
4
Max
message
size
5
6
SHA
0
SHA
1
SHA 2
256/2
24 bits
256
bits
512
bits
512/384
bits
264 -1 bits
264 -1
bits
2128 -1
bits
Word size
32 bits
32 bits
64 bits
Rounds
80
7
Operations
AND, OR,
XOR, shr,
ROT, ADD
(232)
64
AND,
OR,
XOR,
shr,
ROT,
ADD
(232)
8
Security
bits
80
AND,
OR,
XOR,
shr,
ROT,A
DD
(264)
112,
128,
192,
256
<34
(Colli
sions
found)
<63
(Colli
sions
found)
112
128
512 bits
1024
bits
Table 1 and Table 2, shows why SHA-2 is better than other hash
algorithms such as MD-5 and SHA-1.
3.1.3.2 The benefits of SHA-256:
SHA-256 is using here because this 256-bit key is much more
secure than other common hashing algorithms. Without going
into too much technical detail, here are the key benefits of SHA256:
It’s a secure and trusted industry standard: SHA-256
is an industry standard that is trusted by leading
public-sector agencies and used widely by technology
leaders.
Collisions are incredibly unlikely: There are
2256 possible hash values when using SHA-256, which
makes it nearly impossible for two different documents
to coincidentally have the exact same hash value.
The avalanche effect: Unlike some older hashing
algorithms, even a very minor change to the original
information completely changes the hash value—what
is known as an avalanche effect.
3.1.4 Digital Signature Algorithm (DSA)
DSA stand for Digital Signature Algorithm. It is one of the
Federal Information Processing Standard for making digital
signatures, based on mathematical concept of modular
exponentiation and discrete logarithm. It is used for digital
signature and its verification. It was developed by National
Institute of Standards and Technology (NIST) in 1991.
It involves four operations:
1. Key Generation
2. Key Distribution
3. Signing
4. Signature Verification
A digital signature is a technique that binds a person or entity to
the digital data of the signature. Now, this will binding can be
independently verified by the receiver as well as any third party
to access that data. It is a cryptographic value that is calculated
from the data and a secret key known only by the signer or the
person whose signature is that.
Why Blowfish, RSA and SHA-256 have been used in this
proposed system?
Blowfish is an incredibly fast cipher that has a relatively simple
structure and is very effective. It generates a really large key
and this alone is a huge benefit to security. With the increase in
speed of computer processing, Blowfish is able to create a much
longer key so that it is much more difficult to try to hack the key
value. And the way that it generates sub-keys means that each
pair of sub-keys changes slightly. This prevents attackers from
figuring out how the sub-keys were generated, and then gaining
access to all the other known keys. In fact, Blowfish is
especially solid against attacks because of the complexity of the
sub key generation process. It does take longer for the sub keys
to be generated, but for the security-conscious, it is time well
spent. For each key, the encryption routine runs 522 times.
Blowfish has gone through a great deal of analysis and testing to
prove its merit. In fact, since it is license-free and available free
for all uses, its creator encourages hacking attempts. The results
of attempted hacking are posted for others to review and
comment upon; the encryption method can then be tweaked as
needed to ensure its continued success against the bad guys. The
Blowfish algorithm is still relevant and firmly holds its position
as the fastest. In terms of decryption of data, the blowfish
algorithm lacks some speed. Apart from this minor issue, it is
the best, and every network administrator and software
developer must know how to implement it with their work and
code.
The RSA algorithm is the basis of a cryptosystem, a suite of
cryptographic algorithms that are used for specific security
services or purposes which enables public key encryption and is
widely used to secure sensitive data, particularly when it is
being sent over an insecure network such as the internet. It is
extremely elegant, simple, and well-tested. Current commonly
used RSA key lengths include 1024 and 2048 bits.
The main reason technology leaders use SHA-256 is that it
doesn't have any known vulnerabilities that make it insecure and
it has not been ―broken‖ unlike some other popular hashing
algorithms.
3.1.5 Encryption:
Encryption process converts the original data into cipher data
with the help of Blowfish algorithm. Blowfish algorithm is a
symmetric key cryptography method, which uses secret key to
encrypt the original data and send this key with encrypted data
to the receiver. The risk involved in symmetric cryptography is
the shifting of secret key over the internet. To overcome the risk
of symmetric cryptography, RSA algorithm is used which is an
asymmetric key cryptography method.
Blowfish algorithm is responsible for encryption of data, which
is selected by the user. Blowfish is a symmetric cryptographic
algorithm which uses single key to encrypt and decrypt the
original data. This single key is known as secret key. Secret key
is transmitted with encrypted data over the internet and hence
need to encrypt the secret key. This secret key is encrypted
using RSA algorithm, which is an asymmetric cryptographic
algorithm. RSA algorithm uses different key for encryption and
decryption.
Signature generation phase provides the message authentication
with the help of Digital signature using SHA-256. For secure
transmission and authorization, digital signature is used. Digital
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
signature assures that the data is authorized by authenticated
person; it is not modified by any third person during data
transmission. Private Key is used for digital signature on
message digest. Message digest is produced by applying Secure
Hash Algorithm-256 (SHA-256) on encrypted user data.
(iv)
3.1.6 Decryption:
In decryption process cipher data is converted into original data.
In this cryptography method first phase is hybrid decryption
phase and second phase is signature verification phase. Hybrid
decryption phase is a reverse process of hybrid encryption
phase. This phase is responsible for decryption of encrypted
message with the help of RSA and Blowfish. First step, RSA
decryption algorithm decrypts the encrypted key, which helps to
get original data. Second step, with the help of decrypted key
blowfish decryption algorithm decrypt the encrypted data.
In signature verification phase, message digest is generated
using SHA-256 to verify the signature.
(v)
algorithm, which uses pair of key for encryption and
decryption.
CK = CR(K)
Apply SHA-256 (S) on encrypted file Cf to generate
message digest (mD) or hash code. SHA stands for
Secure Hash Algorithm, which is used to generate the
message digest.
mD = S(Cf)
Apply digital signature algorithm (d) on message digest
to generate digital signature (Ds).
Ds = d(mD)
3.2.2 Decryption process:
Decryption process converts the cipher text into original data, so
that user can read or access this data. Only authorized user can
decrypt the cipher text or in other word only authorized user can
access the data.
3.2 Proposed hybrid cryptography algorithm
The proposed hybrid cryptography algorithm consists of two
processes one for encryption and the second for decryption, and
it will be presented as following:
3.2.1 Encryption process:
Basic function of this process is to encrypt the user data to
protect data from unauthorized access or hackers in cloud at the
time of data transmission also. After encryption data will
convert into cipher text.
(i) Select a secret key K between the ranges of 32 bits to
512 bits of variable length.
(ii) Encrypt (C) the selected file f, by applying Blowfish
algorithm (B) with the help of secret key. Blowfish
algorithm is a symmetric key cryptographic algorithm,
which uses single key to convert the original data into
cipher data and vice versa. This key is known as secret
key or private key. It has a 64 bit block size and the
length of key is from 32 bits to 448 bits.
Cf = CBK(f)
Fig 8: Decryption Process
(i)
To get the secret key K, decrypt the encrypted secret
key CK by applying RSA decryption algorithm (PR).
K= PR(CK)
(ii) Using above secret key, obtain the original file f, by
applying blowfish decryption algorithm (PB) on
encrypted file Cf.
f = PBK (Cf)
(iii) Apply verification algorithm (V) of digital signature on
digital signature (Ds) to get the expected message
digest (mD) or hash code.
mD = V(Ds)
(iv) Compare this message digest or hash codes with the
SHA-256 (S) generated message digest or hash code.
mD = S(Cf)
Fig 7: Encryption Process
(iii) Encrypt the secret key K, using RSA algorithm (R).
RSA algorithm is an Asymmetric key cryptographic
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International Journal of Computer Applications (0975 – 8887)
Volume 183 – No. 44, December 2021
4. COMPARISON WITH THE EXISTING
METHODS
Table 3. Comparison between existing and proposed
cryptography algorithms.
Block
Authors Algorithm Key size
Rounds Security
size
Ali E.Taki El
128 bits,
Medium
AES, DES
128 bits 10,12,14
Deen
56 bits,
Security
Jain and
DES,
56 bits,
Medium
64 bits
16
Agrawal
IDEA
128 bits
Security
128 bits,
AES,
Najar and
1024 bits
Medium
RSA,
128 bits 10,12,14
Dar
and 160
Security
SHA-1
bits
Sunita Rani
Ceaser
Highly
and Ambrish cipher,
Secure
Gangal
RSA
Jasleen Kaur
1024
RSA,
Medium
and Dr.
bits, 32– 64 bits
16
Blowfish
Security
Sushil Garg
448 bits
32–448
Proposed
64 bits,
Blowfish,
bits,
hybrid
470
RSA and 4096 bits
Cryptography
bits,
SHA-256 and 256
algorithm
512 bits
bits
64
Highly
Secure
4.1 Advantages of proposed hybrid
cryptography algorithm:
Combination of symmetric cryptography (Blowfish),
asymmetric cryptography (RSA), and hash function
(SHA-256), this proposed method provides a very high
level of security, performance and better key
management.
The proposed method will protect the user data, from
unauthorized access at the time of transmission.
Proposed system increased the difficulty level for
unauthorized person or hacker to decrypt the encrypted
data, through encrypted key, via RSA.
Makes use of digital signatures for message
authentication.
5. CONCLUSION AND FUTURE WORK
The hybrid cryptography algorithm is proposed using Blowfish,
RSA, and SHA-256 algorithms. The combination of symmetric
and asymmetric algorithm provides efficiency to proposed
system. This hybrid algorithm is secure and authentication
IJCATM : www.ijcaonline.org
enabled process which provides high security for cloud
computing by using SHA-256 algorithm.
As a future work, this hybrid algorithm can be constructed from
different existence algorithms to improve the encryption and
decryption process and compare it with this current work.
6. REFERENCES
[1] Mahavir Jain, and Arpit Agrawal, ―Implementation of
Hybrid Cryptography
Algorithm‖, International journal
of Core Engineering & Management, Volume 1, Issue 3,
pp. 1-8, June 2014.
[2] Sunita Rani and Ambrish Gangal, ―Cloud Security with
Encryption using
Hybrid Algorithm and Secured
Endpoints‖, (IJCSIT) International Journal of Computer
Science and Information Technologies, Vol. 3 (3) , 2012.
[3] Ali E.Taki El_Deen, ―Design and Implementation of
Hybrid Encryption Algorithm‖, International Journal of
Scientific & Engineering Research, Volume 4, Issue 12,
pp. 669-673, December- 2013.
[4] Jasleen Kaur and Dr. Sushil Garg, ―Security in Cloud
Computing using Hybrid of Algorithms‖ International
Journal of Engineering Research and General Science
Volume 3, Issue 5, September October, 2015.
[5] Jan Mohammad Najar, and Shahid Bashir Dar, ―A New
Design of a Hybrid
Encryption Algorithm‖,
International Journal of Engineering and Computer
Science, Volume 3, Issue 11, pp. 9169-9171, November
2014.
[6] Self-study: Cryptography and its Types, retrieve from:
https://www.geeksforgeeks.org/cryptography-and-itstypes/, retrieve date: 5 July 2020.
[7] Self-study:
Cloud
computing,
retrieve
from:
https://en.wikipedia.org/wiki/Cloud_computing,
retrieve
date: 1October 2020.
[8] Self-study: RSA (Rivest Shamir Adleman) algorithm,
retrieve from: https://www.educative.io/edpresso/what-isthe-rsa-algorithm, retrieve date: 10 February 2021.
[9] Self-study: Encrypting data with the Blowfish algorithm,
retrieve from: https://www.embedded.com/encryptingdata-with-the-blowfish-algorithm , retrieve date: 13 March
2021.
[10] Self-study: Secure Hash Algorithm 2 (SHA-2), retrieve
from:
https://en.wikipedia.org/wiki/SHA-2, retrieve
date: 18 April 2021.
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Tahera Begum