COMPARATIVE ANALYSIS OF CRYPTOGRAPHIC ALGORITHMS

Abstract

Cryptography is the study of Secret (crypto-) writing (-graphy) that is concealing the content of message from all except the sender and the receiver and to authenticate the correctness of message to the recipient. Data security is the challenging issue of today that touches many areas including computers and communication. Recent cyber security attacks have certainly played with the sentiments of the users. Cryptography is one such way to make sure that confidentiality, authentication, integrity, availability and identification of user data can be maintained as well as security and privacy of data can be provided to the user. We have analysed three algorithms DES, Triple DES and RSA. DES and Triple DES is symmetric key cryptographic algorithm and RSA is an asymmetric key cryptographic algorithm, they have been analysed on their ability to secure data, time taken to encrypt data and throughput the algorithm requires. Performance of different algorithms is different according to the inputs

Full text

Singh et al., International Journal of Advanced Engineering Technology E-ISSN 0976-3945
Int J Adv Engg Tech/IV/III/July-Sept.,2013/16-18
Research Paper
COMPARATIVE ANALYSIS OF CRYPTOGRAPHIC
ALGORITHMS
Mohit Marwaha, Rajeev Bedi, *Amritpal Singh, Tejinder Singh
Address for Correspondence
1,2,3
Assistant Professor, BCET, Gurdaspur,
4
Assistant Professor, Global Institute of Management, Amritsar
ABSTRACT
Cryptography is the study of Secret (crypto-) writing (-graphy) that is concealing the content of message from all except the
sender and the receiver and to authenticate the correctness of message to the recipient. Data security is the challenging issue
of today that touches many areas including computers and communication. Recent cyber security attacks have certainly
played with the sentiments of the users. Cryptography is one such way to make sure that confidentiality, authentication,
integrity, availability and identification of user data can be maintained as well as security and privacy of data can be
provided to the user. We have analysed three algorithms DES, Triple DES and RSA. DES and Triple DES is symmetric key
cryptographic algorithm and RSA is an asymmetric key cryptographic algorithm, they have been analysed on their ability to
secure data, time taken to encrypt data and throughput the algorithm requires. Performance of different algorithms is
different according to the inputs
Keywords: Cryptography, Encryption, DES, RSA, Triple DES, Throughput.
INTRODUCTION
Cryptography is a word with Greek origins, means
“secret writing”. However it is the science and art to
transform the messages to make them secure and
immune against security attacks. It is the technique to
provide secure communication in presence of
adversaries to maintain information securities such as
data confidentiality, data integrity, authentication,
and non-repudiation. The process to convert ordinary
information or the plain text into unintelligible text or
the cipher text in cryptography is called encryption.
The cipher text is understandable only to someone
who knows how to decrypt it. The message or
information is encrypted using an encryption
algorithm. This is usually done with the use of
an encryption key, which specifies how the message
is to be encoded. Any adversary that can see the
cipher text should not be able to determine anything
about the original message. An authorized party,
however, is able to decode the cipher text using
a decryption algorithm which usually requires
a secret decryption key. Encryption schemes are
divided into two groups:
Symmetric-key
In this scheme same key is used for encryption and
decryption it is also known as the secret key
encryption
Asymmetric key
In this scheme different keys are used for encryption
and decryption it is also known as the public-key
encryption.
COMPARISON OF ALGORITHMS
DES
Data Encryption Standard is based on a cipher known
as the Feistel block cipher. This was a block cipher
developed by the IBM cryptography researcher Horst
Feistel in the early 70’s. It consists of a number of
rounds where each round contains bit-shuffling, non-
linear substitutions (S-boxes) and exclusive OR
operations. It encrypts the data in block size of 64
bits each. Same algorithm and key are used for
encryption and decryption. Key is 56 bits long. The
position of 8, 16,24,32,40,48,56,64 are discarded [6].
DES is based on two fundamental attributes of
cryptography Diffusion (Substitution) and Confusion
(Permutation) consisting of 16 rounds. In each round
key and data bits are shifted, permuted, XORed and
sent through, 8 s-box. In the first round 64 bit
plaintext is handed to initial permutation(IP).Then IP
generates two halves left plaintext(LPT)and right
plaintext(RPT).Each LPT and RPT goes through 16
rounds. At the last LPT and RPT are rejoined.
Decryption is same process perform rounds in reverse
order.
Algorithm
[1] DES takes an input of 64-bit long plaintext and
56-bit key (8 bits of parity) and generates
output of 64 bit block.
[2] The plaintext block is subject to an shift the bits
around.
[3] The 8 parity bits are removed from the key by
subjecting the key to its Key Permutation.
[4] The plaintext and key are processed in 16 rounds
consisting of:
a. The key is split into two 28 bit halves
b. Each half of the key is shifted (rotated) by one or
two bits, depending on the round.
c. The halves are recombined and subject to a
compression permutation to reduce the key from
56 bits to 48 bits. This compressed key is used to
encrypt this round's plaintext block.
d. The rotated key halves from step 2 are used in
next round.
e. The data block is split into two 32-bit halves.
f. One half is subject to an Expansion Permutation
to increase its size to 48 bits.
g. Output of step 6 is exclusive-OR'ed with the 48-it
compressed key from step 3.
h. Output of step 7 is fed into an S-box, which
substitutes key bits and reduces the 48-bit block
back down to 32-bits.
i. Output of step 8 is subject to a P-box to permute
the bits.
j. The output from the P-box is exclusive- OR'ed
with other half of the data block.
k. The two data halves are swapped and become the
next round's input.
Figure 1: Working of DES algorithm.

Singh et al., International Journal of Advanced Engineering Technology E-ISSN 0976-3945
Int J Adv Engg Tech/IV/III/July-Sept.,2013/16-18
Triple DES
As an enhancement of DES, the3DES (Triple DES)
encryption standard was proposed. In this standard
the encryption method is similar to the one in original
DES but applied 3 times to increase the encryption
level [8]. It was used to remove the meet-in-the-
middle attack occurred in 2-DES and the brute force
attacks in DES. It also has the advantage of proven
reliability and a longer key length that eliminates
many of the shortcut attacks that can be used to
reduce the amount of time it takes to break DES.
Figure 2: Working of Triple DES algorithm.
RSA
This is public key encryption algorithm developed by
Ron Rivest, Adi Shamir and Len Adlemen in 1977. It
is most popular and asymmetric key cryptographic
algorithm. It may used to provide both secrecy and
digital signature [2]. It uses the prime no. to generate
the public and private key based on mathematical fact
and multiplying large numbers together. It uses the
block size data in which plaintext and cipher text are
integers between 0and n1 for some n values. Size of n
is considered 1024bits or 309 decimal digits. In this
two different keys are used for encryption and
decryption purpose. As sender knows encryption key
and receiver knows decryption key.
Algorithm
Choose large prime numbers p and q such that p~=q.
Compute n=p*q
Compute φ (pq) = (p-1)*(q-1)
Choose the public key e such that
gcd (φ (n), e) =1; 1<e< φ (n)
Select the private key d such that
d*e mod φ (n) =1
So in RSA algorithm encryption and decryption are
performed as-
Encryption
Calculate cipher text C from plaintext message M
such that
C=M ^e mod n
Decryption
M=C^d mod n=M^ed mod n
Comparative analysis of algorithms
We have studied different techniques used for
fulfilment of data encryption purpose. There are
some comparisons generated on different important
features such as:
Input data size- Different algorithm required
different memory space to perform the operation. The
memory space required by any algorithm is
determined on the basis of input data size, number of
rounds etc. The algorithm is considered best which
use small memory and perform best task.
Time- The time required by algorithm to complete
the operation depends on processor speed, algorithm
complexity. Less the time algorithm takes to
complete its operation better it is.
Throughput-Throughput of the encryption
algorithms is calculated by dividing the total plaintext
in Megabytes encrypted on total encryption time for
each algorithm.
Thus, if throughput increased the power consumption
is decreased.
Theoretical Analysis
The theoretical analysis is as follow:
Simulation Analysis
We have used Java and ASP.net for simulation. We
have taken two parameters time and memory for the
simulation setup and calculated throughput by
dividing the total plaintext encrypted on total
encryption time for each algorithm. We have
calculated time taken by each algorithm in
milliseconds and calculated memory by subtracting
size of original data from encrypted data.
The Tables below represents the speed of RSA,
Triple DES and DES algorithm to encrypt the data of
same length [1]. Throughput of the encryption
algorithms is calculated by dividing the total plaintext
in Megabytes encrypted on total encryption time for
each algorithm. Thus, if the throughput increased
than power consumption decreased. So, as speed of
the DES encryption is twice the speed of RSA
encryption speed. And DES also consumes small
power as comparison to RSA power. Finally, Triple
DES still requires more time than DES because DES
encrypts the data once and Triple DES encrypts the
data three times. Triple DES has more power
consumption and fewer throughputs than the DES
due to its triple phase characteristics. It had been also
observed that decryption of DES algorithm is better
than other algorithms in throughput and less power
consumption. But the aspect the DES and RSA lacks
that make Triple DES as our choice of algorithm is
security.
Table1: Execution Time (Milliseconds) of Encryption of
different data packet size
Table2: Execution Time (Milliseconds) of Decryption of
Different data packet size

Singh et al., International Journal of Advanced Engineering Technology E-ISSN 0976-3945
Int J Adv Engg Tech/IV/III/July-Sept.,2013/16-18
CONCLUSION
The advantage of proven reliability and a longer key
length that eliminates many of the attacks that can be
used to reduce the amount of time it takes to break
DES. Confidentiality and scalability provided by
Triple DES over RSA and DES is much higher that
makes it suitable even though DES consume less
power memory and time to encrypt and decrypt the
data but on security front DES can be easily broken
by brute force technique as compared to Triple DES
and RSA making it the least secure algorithm .
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