Enhancement of DES Algorithm with Multi State Logic

International Journal of Research in Computer Science
eISSN 2249-8265 Volume 4 Issue 3 (2014) pp. 13-17
www.ijorcs.org, A Unit of White Globe Publications
doi: 10.7815/ijorcs.43.2014.085
ENHANCEMENT OF DES ALGORITHM WITH
MULTI STATE LOGIC
Payal Patel1
, Kruti Shah2
, Khushbu Shah3
1
M.E. Computer Engineering, L.J. Institute of Engineering & Technology, Ahmedabad, INDIA
Email: payal.5886@gmail.com
2
Asst. Prof. BITS, EDU Campus Varnama, Vadodara, INDIA
Email: kruti13shah@gmail.com
3
Asst. Prof. L.J. Institute of Engineering & Technology, Ahmedabad, INDIA
Email: khushburana1@gmail.com
Abstract: The principal goal to design any encryption
algorithm must be the security against unauthorized
access or attacks. Data Encryption Standard
algorithm is a symmetric key algorithm and it is used
to secure the data. Enhanced DES algorithm works on
increasing the key length or complex S-BOX design or
increased the number of states in which the
information is to be represented or combination of
above criteria. By increasing the key length, the
number of combinations for key will increase which is
hard for the intruder to do the brute force attack. As
the S-BOX design will become the complex there will
be a good avalanche effect. As the number of states
increases in which the information is represented, it is
hard for the intruder to crack the actual information.
Proposed algorithm replace the predefined XOR
operation applied during the 16 round of the standard
algorithm by a new operation called “Hash function”
depends on using two keys. One key used in “F”
function and another key consists of a combination of
16 states (0,1,2…13,14,15) instead of the ordinary 2
state key (0, 1). This replacement adds a new level of
protection strength and more robustness against
breaking methods.
Keywords: DES, Encryption, Decryption
I. INTRODUCTION
Cryptography is usually referred to as - the study of
secret, while now a days is most attached to the
definition of encryption. Encryption is the conversion
of data into a form, called cipher text that cannot be
easily understood by unauthorized people. Decryption
is the process of converting encrypted data back into
its original form, so it can be understood. It is the
easiest and most practical method of protecting
data stored or transmitted electronically and is
particularly essential with sensitive data.
Encryption uses a mathematical algorithm to
scramble readable text that cannot be read unless the
reader has the key to "unlock," or convert, the
information back to its readable form. This means that
your sensitive data cannot be accessed without you
providing a password. Even a single failure to encrypt
a sensitive data whether through an e-mail, via a stolen
flash drive or laptop, can result in a security breach
with criminal or civil liabilities and irreparable harm
to finances and the reputation of the university.
Figure 1: Encryption/Decryption
II. DATA ENCRYPTION STANDARD
Data Encryption Standard (DES) is a widely-used
method of data encryption using a private (secret) key.
DES applies a 56-bit key to each 64-bit block of data.
The process can run in several modes and involves 16
rounds or operations. Although this is considered
"strong" encryption, many companies use "triple
DES", which applies three keys in succession. DES
originated at IBM in 1977 and was adopted by the
U.S. Department of Defense. It is specified in
the ANSI X3.92 and X3.106 standards and in the
Federal FIPS 46 and 81 standards.
The algorithm is best suited to implementation in
hardware, probably to discourage implementations in
software, which tend to be slow by comparison.
However, modern computers are so fast that
satisfactory software implementations are readily
available. DES is the most widely used symmetric
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14 Payal Patel, Kruti Shah, Khushbu Shah
algorithm in the world, despite claims that the key
length is too short. Ever since DES was first
announced, controversy has raged about whether 56
bits is long enough to guarantee security.
Figure 2: DES Algorithm [7]
1. Expansion (E): The 32-bit input word is first
expanded to 48 bits by duplicating and reordering
half of the bits.[4]
2. Key mixing: The expanded word is XORed with a
round key constructed by selecting 48 bits from the
56-bit secret key, different selection is used in each
round.
Figure 3: Modified DES Algorithm
3. Substitution: The 48-bit result is split into eight 6-
bit words which are substituted in eight parallel
6x4-bit S-boxes. All eight S-boxes are different but
have the same special structure.
4. Permutation (P): The resulting 32 bits are
reordered according to a fixed permutation before
being sent to the output.
The modified R Block is then XORED with L Block
and the resultant fed to the next R Block register. The
unmodified R Block is fed to the next L Block
register. With another 56 bit derivative of the 64 bit
key, the same process is repeated.[2]
1. The plaintext block is subject to an Initial
Permutation to shift the bits around.
2. The 8 parity bits are removed from the key by
subjecting the key to its Key Permutation.
3. The plaintext and key are processed in 16
rounds consisting of:
3.1. The key is split into two 28-bit halves.
3.2. Each half of the key is shifted (rotated) by one
or two bits, depending on the round.
3.3. 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.
3.4. The rotated key halves from step 2 are used in
next round.
3.5. The data block is split into two 32-bit halves.
3.6. One half is subject to an Expansion
Permutation to increase its size to 48 bits.
3.7. Output of step 6 is exclusive-OR with the 48-
bit compressed key from step 3.
3.8. 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.
3.9. Output of step 8 is subject to a P-box to permute
(scramble) the bits.
3.10.The output from the P-box is exclusive-OR with
the other half of the data block.
3.11.The two data halves are swapped and become
the next round's input.
4.After 16 rounds, the resultant chipper text is subject
to Reverse Initial Permutation. The output is the
cipher text block.
III. ENHANCED DES ALGORITHM
A new method to enhance the performance of the
Data Encryption Standard (DES) algorithm. This is
done by replacing the predefined XOR operation
applied during the 16 round of the standard algorithm
by a new operation depends on using two keys, each
key consists of a combination of 4 states (0, 1, 2, 3)
instead of the ordinary 2 state key (0, 1). This
replacement adds a new level of protection strength
and more robustness against breaking methods.
The new operation needs 3 inputs, the first one
specify the table number that should be used to
calculate the result among the 4 tables, the other 2
inputs define the row and column number in the
specified table where the cross point of them gives the
result.[3]
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Enhancement of DES Algorithm with Multi State Logic 15
IV. PROPOSED DES ALGORITHM
This research proposed a new improvement to the
DES algorithm. The 64 bit data of the plain text
message is input to the initial Permutation Function
(IP). The initial permutation is rearranging the bits.
Output of IP is divided into two halves. One is left half
‘L’ and another is right half ‘R’. Each half is
consisting of 32 bits. Right half is input to the
Expansion Function. R input is first expanded to 48
bits by using a table that defines a permutation plus an
expression that involves duplication of 16 of the R
bits. The resulting 48 bits are XORed with Ki, which
consist of 48 bit.
Initially Ki is 64 bit key from which each 8th
parity bit of each byte is discarded, which is the
Permuted Choice-1 function. And key will become of
56 bits. 56 bit key is divided into two halves. Left half
which is Ci and Right half is Di. At each round Ci and
Di are separately subjected to a circular left shift,
rotation, of 1 or 2 bits. Shifted values serve as input to
the next round. Now shifted Ci and shifted Di will be
the input to the Permuted Choice-2 function. Output of
Permuted Choice-2 function is 48 bit, which is the
input to the XOR function.
The output of XORed is 48 bits which the input to
the Substitution Function. Output of this function is 32
bit. The substitution function is consists of 6 S-BOX.
Each S-BOX has 8 bit of input and 32 bit of output.
Perform the XOR operation between the first and
second S-BOX output. Output of XOR operation is
XORed with the output of the 3rd S-BOX. And output
of XOR operation is XORed with the output of 4th S-
BOX. Output of this XOR operation is XORed with
the output of the 5th S-BOX. Output of the XOR
operation is XORed with the 6th S-BOX output.
From the input to the Expansion to the output of
last ADD operation is worked as “F” Function.
Algorithm of modified data encryption standard
with 16 state operations is given below. [7]
INPUT: plaintext m1…m64; 64-bit two keys K=k1….
k64 and K’=k1’….k64’ (includes 8 parity bits).
OUTPUT: 64-bit cipher text block C=c1…c64.
1. (key schedule) Compute sixteen 48-bit round keys Ki,
from K.
1.1. (key schedule) compute sixteen 32-bit round keys
KI
’
, from K’
2. (L0, R0) ← IP (m1, m2, … m64) (Use IP Table to
permute bits; split the result into left and right 32-bit
halves L0=m58m50… m8,R0=m57m49… m7)
3. (16 rounds) for i from 1 to 16, compute Li and Ri as
follows:
3.1. Li=Ri-1
3.2. Ri = Li-1 # f (Ri-1, Ki)
Where, f(Ri-1, Ki) = P(S(E(Ri-1) Å Ki)), computed as
follows:
a. Expand Ri-1 = r1r2 . . . r32 from 32 to 48 bits.
T ← E(Ri-1). (Thus T= r32r1r2 . . . r32r1.)
b. T' ← T XOR Ki . Represent T’
as eight 6-bit
character strings:
T’
= (B1 . . . B8)
c. T”
← F where Function F = ((((((( S1+S2) mod 2 ^
32) XOR S3) + S4) mod 2^32) XOR S5) +S6)mod
2^32 Here, Si(Bi) maps to the 8 bit entry in row r
and column c of Si
d. T''' ← P(T''). (Use P per table to permute the 32 bits
of T''=t1, t2 ….. t32, yielding t16t7 . . . t25.) and the
operation # in Ri = Li-1 # f (Ri-1, Ki) is computed as
follows:
I. Convert the 32 bits resulted from f (R i-1, Ki)
into 16-states 8 digits call it ‘f’.
II. Convert the 32 bits of Li-1 to 16-states 8 digits
call it Li-1'
III. Convert the 32 bits of Ki' to 16-states 8 digits
call it Ki''
IV. Compute Ri by applying the # operation on f ',
Li-1', and Ki'' according to truth tables shown in
Table.
4. b1b2 . . . b64 ← (R8, L8). (Exchange final blocks L8,
R8.)
5. C ← IP-1
(b1b2 . . . b64). (Transpose using IP-1
C =
b40b8 . . . b25.)
6. End.
Proposed model of Enhanced Multi State DES
Algorithm is shown below.
Figure 4: Proposed Model
www.ijorcs.org

16 Payal Patel, Kruti Shah, Khushbu Shah
Let’s take one example using proposed
algorithm. Our Input Message is 41427A36313E5254
which is our plain text is converting into cipher text
using this proposed algorithm. Here, there are 16
rounds for convert plain text to cipher text. In each
round it contain two keys. First we convert plain text
into binary format also we have to convert key into
binary format which is also in hex format. Now,
performing all operation of this proposed algorithm
and get the cipher text.
The substitution function is consists of 6 S-BOX.
Each S-BOX has 8 bit of input and 32 bit of output.
Perform the XOR operation between the first and
second S-BOX output. Output of XOR operation is
XORed with the output of the 3rd S-BOX. And output
of XOR operation is XORed with the output of 4th S-
BOX. Output of this XOR operation is XORed with
the output of the 5th S-BOX. Output of the XOR
operation is XORed with the 6th S-BOX output.
Step 1. keys: K = 4135235951463231
Data: P =41427A36313E5254
Step 2. Initial Permutation of Message which is given
by User.
Step 3. for i =1 to 16 round
Ln = Rn-1
Rn = Ln-1 # f(Rn-1,Kn)
Step 4. After complete one round we got
F1 = R1 = EA67369D
L1 = 11A8FCC7
At the end of 16th
round, Inverse Permutation is
10000011 00010011 01011011 01101000
11001001 01101000 00001111 01101010
So, finally we got our cipher text
41CA793E91BE7074.
V. RESULTS & COMPARISION
Compare proposed enhanced multi state DES
algorithm with original des algorithm, we got good
avalanche effect and also solve cryptanalysis attack.
Figure 5: Avalanche effect of 64 bit of input Data for DES
and Enhanced DES with multi state logic
Figure 6: 64 bit of input key for DES and Enhanced DES
with multi state logic
Figure 7: SAC of ‘F’ Function for DES and Enhanced DES
with multi state logic
VI. CONCLUSION
The volume of information exchanged by
electronic means such as internet, wireless phones,
Fax, etc. is increasing very rapidly. It is very serious
that information through internet, an enormous
computer network, is vulnerable to hackers and that
privacy of wireless phones without security can be
invaded. We should develop improved
cryptosystems to provide greater security.
Proposed algorithm in this paper has been
designed the DES-like cryptosystem called the
Enhanced Multi State DES. It extends the DES
algorithm so that the iterative number of the f
function during the full 16 round of each sub-block
is different, in order to decrease the probability of
the full 16 round characteristic against the
differential cryptanalysis. Summary of Enhanced
algorithm are:
i. Creating the S-BOX design as complex as possible
so it will create the good avalanche effect. Because
in S-Box design there is a 8 bit of input and 32 bit
of output.(Extra 24 bits)
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Enhancement of DES Algorithm with Multi State Logic 17
ii. Number of combination of key 256
* 232
to decipher
plaintext. It hard to do brute force attack.
iii. Increasing the number of states for presenting the
information, will increasing the number of
combination of the information so it will be the
hard for the intruder to detect the actual
information.
iv. Value extracted from hash table is depends on the
plaintext message, not any particular pattern.
VII. REFERENCES
Journals
[1] Dr. Mohammed M. Alani College of Computer
Engineering and Sciences, Gulf University, Kingdom of
Bahrain, “DES96 - Improved DES Security”, 7th
International Multi-Conference on Systems, Signals and
Devices, IEEE 2010.
[2] Akhil Kaushik Assistant Professor, Computers
Department, Manoj Bamela Assistant Professor,
Electronics Department, AnantKumar B.Tech Pre-final,
Computers Engineering from T.I.T&S College Bhiwani,
Haryana, India, “Block Encryption Standard for Transfer
of Data”, International Conference on Networking and
Information Technology, IEEE 2010.
[3] K. Anchugam and M. Tamilselvi, “New Data Encryption
Standard Algorithm”, IJCSNS International Journal of
Computer Science and Network Security, VOL.13 No.4,
April 2013.
[4] Prashanti G.,Dipti S, Sandhya Rani K., “A Novel
Approach for Data Encryption Standard Algorithm”,
International Journal of Engineering and Advanced
Technology (IJEAT) ISSN: 2249 – 8958, Volume-2,
Issue-5, June 2013.
[5] Devendra Kumar Malakar, Prof. Dineshchandra
Jain,CSE Department, Shri Vaishnav Institute of
Technology and Science,Indore, Madhya Pradesh,India,
“The Problem Analysis on Encryption Techniques in
Cryptography” , International Journal of Societal
Applications of Computer Science Vol 2 Issue 5 May
2013,ISSN 2319 – 8443.
Conferences
[6] M. A. Al Zain and E. Pardede, “Using Multi Shares for
Ensuring Privacy in Database-as-a-Service”, 44th
Hawaii,
International Conference on System Sciences
(HICSS),2011,pp 1-9. doi: 10.1109/HICSS.2011.478
Books
[7] W. Stallings, “Cryptography and Network Security:
Principles and Practices, 4th ed., Prentice Hall”.
Website
[8] https://engineering.purdue.edu/kak/compsec/NewLecture
s/Lecture8.pdf
How to cite
Payal Patel, Kruti Shah, Khushbu Shah, “Enhancement of DES Algorithm with Multi State Logic”. International
Journal of Research in Computer Science, 4 (3): pp. 13-17, May 2014. doi: 10.7815/ijorcs.43.2014.085
www.ijorcs.org

Enhancement of DES Algorithm with Multi State Logic

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