Implementation of-hybrid-cryptography-algorithm

ISSN: 2348 9510
International Journal Of Core Engineering & Management(IJCEM)
Volume 1, Issue 3, June 2014
126
Implementation Of Hybrid Cryptography Algorithm
Mr. Mahavir Jain
1
M.E. Student, IET DAVV Indore, M.P.
E-mail id:- e2zinfo@gmail.com
Mr. Arpit Agrawal
Asst. Professor, IET DAVV Indore, M.P.
Abstract
Internet is a public-interacted system; the amount of information exchanged over the
internet is completely not safe. Protecting the information transmitted over the network is a
difficult task and the data security issues become increasingly important. In recent years, a
controversy has arisen over so-called strong encryption. This refers to ciphers that are
essentially unbreakable without the decryption keys. While most companies and their
customers view it as a means of keeping secrets and minimizing fraud, some governments
view strong encryption as a potential vehicle by which terrorists might evade authorities.
These governments, including that of the United States, want to set up a key-escrow
arrangement. This means everyone who uses a cipher would be required to provide the
government with a copy of the key. Decryption keys would be stored in a supposedly secure
place, used only by authorities, and used only if backed up by a court order. Opponents of
this scheme argue that criminals could hack into the key-escrow database and illegally
obtain, steal, or alter the keys. Supporters claim that while this is a possibility,
implementing the key escrow scheme would be better than doing nothing to prevent
criminals from freely using encryption/decryption. At present, various types of
cryptographic algorithms provide high security to information on networks, but they are
also have some drawbacks. To improve the strength of these algorithms, we propose a new
hybrid cryptographic algorithm in this paper. The algorithm is designed using combination

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of two symmetric cryptographic techniques. These two primitives can be achieved with the
help of Data Encryption Standard (DES) and International Data Encryption Standard
(IDEA). This new hybrid cryptographic algorithm has been designed for better security
with integrity.
Keywords: cryptography, Encryption, Decryption.
I. INTRODUCTION
In cryptography, a message authentication code is a short piece of information used to
authenticate a message and to detect message tampering and forgery. Here we will study
about DES and IDEA algorithms seperately.
1.1 DES
DES is the archetypal block cipher — an algorithm that takes a fixed-length string of
plaintext bit and transforms it through a series of complicated operations into another
cipher text bit string of the same length. DES also uses a key to customize the
transformation, so that decryption can only be performed by those who know the particular
key used to encrypt. In the case of DES, the block size is 64 bit, but only 56 bit are used
and the remaining 8 bit can be used for parity, and then discarded in the algorithm.
Therefore, the effective key length of DES is 56 bit. The algorithm‟s overall structure is
shown in Fig. 6: there are 16 identical same processes; termed rounds. There is also an
initial and final permutation, known as IP and FP (the FP is inverse function of IP (IP
―revocation‖ FP operations, and vice versa)). Before the main rounds, the block is divided
into two 32 bit half block and processed at same times; this crossing process is known as
the Feistel scheme. Feistel scheme is used to ensure the similarity of both the encryption
and decryption processes. The only difference is the sub-key, which is reversed and used in
decryption process and remaining part it is the same. This design simplifies the algorithm

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implementation, especially for hard implementation. The symbol denotes the (XOR)
operation. The ―F- function‖ scrambles data process with one sub-key, then the output
from F-function doing the XOR operation with other half block data, and the halves are
swapped before the next round. After the final round, the halves are not swapped; this is a
feature of the Feistel structure which makes encryption and decryption similar processes.
1.1.1 Performance Analysis-
DES (Data Encryption Standard) is a symmetric cryptographic algorithm which
was adopted in January 1977 as a standard in the United States by the former National
Bureau of Standards (now known as National Institute of Standards and Technology). It is
widely used for protecting sensitive information‟s and for the authentication of banking
transactions, for example. We propose here to present six different ways to break DES, the
last one being currently analyzed at the LASEC.
1.1.2 Exhaustive key search
DES is an algorithm which encrypts 64 bits blocks of data using a 56 bits secret
key. A common scenario is the following: we have an encrypted block at disposal, we have
some information about the plaintext (we know that it is an ASCII text, or a JPEG image,
for example) and we would like to recover the secret key.
The simpler method is to try to decrypt the block with all the possible keys. The
information we have on the clear text will allow us to recognize the right key and to stop
the search. In average, we will have to try 36'028'797'018'963'968 (36 millions of billions)
of keys. Knowing that a common modern PC can check about one to two millions keys
each second, this represents a work time of about 600 to 1200 years for a single machine.

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1.1.2.1 A dedicated machine
An exhaustive search is quite time consuming for a single PC, but it is possible to
do better. In 1998, the EFF (Electronic Frontier Foundation has built a dedicated machine
in order to show to the world that DES is not (or no more) a secure algorithm. Deep Crack,
that's the name of the machine, costs $200'000 and is built with 1536 dedicated chips. Deep
Crack is able to recover a key with the help of an exhaustive search in 4 days in average,
checking 92 billions of keys each second. Knowing the budget of electronic intelligence
agencies (for example, the National Security Agency in the USA), it is easy to be
pessimistic on the security of DES against such organizations!
1.1.2.2 A huge cluster of computers
One needs not even a lot of money to break DES. Volunteers who are ready to
donate their machine's idle time and the Internet are sufficient. In January
1999, Distributed.Net, an organization specialized in collecting and managing computer's
idle time, broke a DES key in 23 hours! More than 100'000 computers (from the slowest
PC to the most powerful multiprocessors machines) have received and done a little part of
the work; this allowed a rate of 250'000'000'000 keys being checked every second.
1.1.2.3 A time-memory tradeoff
An exhaustive search needs a lot of time, but negligible memory at all. It is now
possible to imagine a scenario: we have a lot of available memory, and we are ready to
recomputed for all the possible keys k the encrypted block y corresponding to a given
block x of data and storing the pairs (y, k). So we will be able to find very quickly the right
key if we have at disposal an encrypted version x' of our known block with an unknown
key k' by searching in this kind of dictionary. This method becomes to be interesting in the
case where we have more than one key to find and we have enough memory at disposal.In

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1980, Martin Hellman proposed in a time-memory tradeoff algorithm, which needs less time than
an exhaustive search and less memory than the storing method. His algorithm needs in the order of
1000 GB of storage possibilities and about 5 days of computations for a single PC.
1.1.2.4 Differential cryptanalysis
In 1990, Biham and Shamir, two Israeli cryptographers working at the Weitzmann
Institute, have invented a new generic technique to break symmetric algorithms called the
differential cryptanalysis. It was the first time that a method could break DES in less time
than an exhaustive search. Imagine that we have a device which encrypts data with a hard-
wired secret key, and imagine furthermore that we don't have the tools needed to "read" the
key in the chip. What we can do is to choose some blocks of data and to encrypt them with
the device. The data analysis phase computes the key by analyzing about 247
chosen
plaintexts. A big advantage of this attack is that its probability of success increases linearly
with the number of available chosen plaintexts and can thus be conducted even with fewer
chosen plaintexts. More precisely, the attack analyses about 214
chosen plaintexts and
succeeds with a probability of 2-33
.
1.1.2.5 Linear cryptanalysis
Another very important generic method to break ciphers is the linear cryptanalysis
which was invented in 1994 by a japanese researcher working at Mitsubishi Electronics,
Mitsuru Matsui. If we have 243
= 8'796'093'022'208 known plaintext-cipher text pairs at
disposal, which represents 64'000 GB of data, it is possible to recover the corresponding
key in a few days using linear cryptanalysis. It is the most powerful attack on DES known
at this time.A current research project at the LASEC is the cost analysis of this attack. We have
first implemented a very fast DES encryption routine using advanced techniques on a common Intel
Pentium III architecture; this routine is able to encrypt at a rate of 192 Mbps on a PIII 666MHz

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processor. We have then implemented the attack; it is currently running on 18 CPU's, breaking a
DES key in 4 days.The goal of this project is to do a better statistical analysis on its complexity and
on its success probability. First experimental and theoretical results have shown that a linear
cryptanalysis needs in reality less time as estimated by Matsui in 1994.
1.2 International Data Encryption Algorithm
The Data Encryption Standard (DES) algorithm has been a popular secret key
encryption algorithm and is used in many commercial and financial applications.Although
introduced in 1976, it has proved resistant to all forms of cryptanalysis. However, its key
size is too small by current standards and its entire 56 bit key space can be searched in
approximately 22 hours. International Data Encryption Algorithm (IDEA) is a block cipher
designed by Xuejia Lai and James L. Massey of ETH-Zürich and was first described in
1991. It is a minor revision of an earlier cipher, PES (Proposed Encryption Standard);
IDEA was originally called IPES (Improved PES). IDEA was used as the symmetric cipher
in early versions of the Pretty Good Privacy cryptosystem.IDEA was to develop a strong
encryption algorithm, which would replace the DES procedure developed in the U.S.A. in
the seventies. It is also interesting in that it entirely avoids the use of any lookup tables or
S-boxes. When the famous PGP email and file encryption product was designed by Phil
Zimmermann, the developers were looking for maximum security. IDEA was their first
choice for data encryption based on its proven design and its great reputation.
The IDEA encryption algorithm
i. provides high level security not based on keeping the algorithm a secret, but rather
upon ignorance of the secret key
ii. is fully specified and easily understood
iii. is available to everybody
iv. is suitable for use in a wide range of applications

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v. can be economically implemented in electronic components (VLSI Chip)
vi. can be used efficiently
vii. may be exported world wide
viii. is patent protected to prevent fraud and piracy
1.2.1 Description of IDEA
The block cipher IDEA operates with 64-bit plaintext and cipher text blocks and is
controlled by a 128-bit key. The fundamental innovation in the design of this algorithm is
the use of operations from three different algebraic groups. The substitution boxes and the
associated table lookups used in the block ciphers available to-date have been completely
avoided. The algorithm structure has been chosen such that, with the exception that
different key sub-blocks are used, the encryption process is identical to the decryption
process.
1.2.2 Key Generation
The 64-bit plaintext block is partitioned into four 16-bit sub-blocks, since all the algebraic
operations used in the encryption process operate on 16-bit numbers. Another process
produces for each of the encryption rounds, six 16-bit key sub-blocks from the 128-bit key.
Since a further four 16-bit key-sub-blocks are required for the subsequent output
transformation, a total of 52 (= 8 x 6 + 4) different 16-bit sub-blocks have to be generated
from the 128-bit key.
The 52 16-bit key sub-blocks which are generated from the 128-bit key are produced as
follows:
i. First, the 128-bit key is partitioned into eight 16-bit sub-blocks which are then directly
used as the first eight key sub-blocks.

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ii. The 128-bit key is then cyclically shifted to the left by 25 positions, after which the
resulting 128-bit block is again partitioned into eight 16-bit sub-blocks to be directly
used as the next eight key sub-blocks.
iii. The cyclic shift procedure described above is repeated until all of the required 52 16-bit
key sub-blocks have been generated.
1.2.3 Encryption
The functional representation of the encryption process is shown in Figure 1. The process
consists of eight identical encryption steps (known as encryption rounds) followed by an
output transformation. The structure of the first round is shown in detail. In the first
encryption round, the first four 16-bit key sub-blocks are combined with two of the 16-bit
plaintext blocks using addition modulo 216
, and with the other two plaintext blocks using
multiplication modulo 216
+ 1. The results are then processed further as shown in Figure 1,
whereby two more 16-bit key sub-blocks enter the calculation and the third algebraic group
operator, the bit-by-bit exclusive OR, is used. At the end of the first encryption round four
16-bit values are produced which are used as input to the second encryption round in a
partially changed order. The process described above for round one is repeated in each of
the subsequent 7 encryption rounds using different 16-bit key sub-blocks for each
combination. During the subsequent output transformation, the four 16-bit values produced
at the end of the 8th
encryption round are combined with the last four of the 52 key sub-
blocks using addition modulo 216
and multiplication modulo 216
+ 1 to form the resulting
four 16-bit ciphertext blocks.
1.2.4 Decryption
The computational process used for decryption of the ciphertext is essentially the same as
that used for encryption of the plaintext. For plaintext exceeding decryption, different 16-

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bit key sub-blocks are generated.More precisely, each of the 52 16-bit key sub-blocks used
for decryption is the inverse of the key sub-block used during encryption in respect of the
applied algebraic group operation. Additionally, the key sub-blocks must be used in the
reverse order during decryption in order to reverse the encryption process. IDEA supports
all modes of operation as described by NIST in its publication FIPS 81. A block cipher
encrypts this fixed size, the simplest approach is to partition the plaintext into blocks of
equal length and encrypt each separately. This method is named Electronic Code Book
(ECB) mode. However, Electronic Code Book is not a good system to use with small block
sizes (for example, smaller than 40 bits) and identical encryption modes. As ECB has
disadvantages in most applications, other methods named modes have been created. They
are Cipher Block Chaining (CBC), Cipher Feedback (CFB) and Output Feedback (OFB)
modes.
2. LITERATURE SURVEY
Modern cryptography originates in the works of Feistel at IBM during the late 1960„s and
early 1970„s. DES was adopted by the NIST, for encrypting unclassified information in
1977. DES is now replaced by the Advanced Encryption Standard (AES), which is a new
standard adopted. Another milestone happened during 1978, marked by the publication of
RSA. The RSA is the first full-fledged public-key algorithm. This discovery by and large
solved the key exchange problem of cryptography. RSA also proposed the world wide
acceptable standard techniques like authentication and electronic signatures in modern
cryptography.
There are various issues related to DES and IDEA. Some of them are as follows

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i. The 56-bit key size is the biggest defect of DES. Chips to perform one million of DES
encrypt or decrypt operations a second are available (in 1993). A $1 million DES
cracking machine can search the entire key space in about 7 hours.
ii. Hardware implementations of DES are very fast; DES was not designed for software
and hence runs relatively slowly.
iii. Brute force is a known-plaintext attack and requires testing, on average, 255
keys.
iv. Differential cryptanalysis is a chosen plaintext attack where the attacker encrypts two
chosen plaintext blocks and uses the differences between the chipper text to deduce the
key. This attack requires 243
plaintext/cipher text pairs and 255.1
encryption operations,
making it less efficient than a brute force attack. Apparently DES was designed to be
resistant to differential cryptanalysis.
2.1 Comparative study between DES and IDEA
Factors DES IDEA
Key length 56 bits 128 bits
Cipher Type Symetric block cipher Symetric block cipher
Block size 64 bits 64 bits
Cryptanalysis resistance Vulunerable Strong
Security Proven inadequate Considered Secure
Possible Keys 256
2128
Time required to check all possible
keys at 50 billions per second
400 days 5*1023 years

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3. PROBLEM DOMAIN
As we have discussed in the various issues section that DES is no more secure for
transmitting data over the network. It is possible to break the key of DES algorithm with
present high performance systems. With 600 million instructions per second we can break
the DES within 8 hours. Further if we consider that in future the speed of computer will
enhance so it will be possible to break the IDEA algorithm also. So here we are proposing a
new hybrid algorithm that is a combination of DES and IDEA. So this hybrid system would
have combined security of both the algorithms.
4. SOLUTION DOMAIN
A Computer Network is an interconnected group of autonomous computing nodes,
which use a well defined, mutually agreed set of rules and conventions known as protocols,
to interact with one-another meaningfully and allow resource sharing preferably in a
predictable and controllable manner. Communication has a major impact on today‟s
business. It is desired to communicate data with high security. With the rapid development
of network technology, internet attacks are also versatile, the traditional encryption
algorithms (single data encryption) is not enough for today‟s information security over
internet, so we propose this hybrid Cryptograph Algorithm. It is a design for transfer data
with better security. At present, various types of cryptographic algorithms provide high
security to information on networks, but there are also has some drawbacks. This hybrid
algorithm is designed for better security by combinations of DES and IDEA.

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Fig. 4.1 various stages of Hybrid cryptography algorithm
4.1 Steps for Hybrid Cryptography algorithm
DES takes an input of 64-bit plaintext data block and 56-bit key (with 8 bits of parity) and
outputs a 64-bit cipher text block.
1. The 8 parity bits are removed from the key by subjecting the key to its Key Permutation.
2. The plaintext and key are processed in 16 rounds consisting of:
The key is split into two 28-bit halves.
i. Each half of the key is shifted (rotated) by one or two bits, depending on the round.
Data Encryption Standard (DES)
64-bit cipher text
International Data Encryption
Standard
(IDEA)
64-bit cipher text
64-bit Plain text

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ii. 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.
iii. The rotated key halves from step 2 are used in next round.
iv. The data block is split into two 32-bit halves.
v. One half is subject to an Expansion Permutation to increase its size to 48 bits.
vi. Output of step 6 is exclusive-OR'ed with the 48-bit compressed key from step 3.
vii. 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.
viii. Output of step 8 is subject to a P-box to permute (scramble) the bits.
ix. The output from the P-box is exclusive-OR'ed with the other half of the data block.
x. The two data halves are swapped and become the next round's input.
3.After 16 rounds, the resultant is cipher text.
4.This resultant cipher text is a input for the IDEA
The 52 16-bit key sub-blocks which are generated from the 128-bit key are produced as
follows:
i. First, the 128-bit key is partitioned into eight 16-bit sub-blocks which are then directly
used as the first eight key sub-blocks.
ii. The 128-bit key is then cyclically shifted to the left by 25 positions, after which the
resulting128-bit block is again partitioned into eight 16-bit sub-blocks to be directly used as
the next eight key sub-blocks.
The cyclic shift procedure described above is repeated until all of the required 52 16-bit
key sub-blocks have been generated.

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5. SYSTEM DOMAIN
This particular algorithm can be implemented in any language like c, c++, java. Here I will
implement this algorithm in java language. It needs no specific hardware and software .
1.1 Software Requirements
i. JDK (Java development kit)
1.2 Hardware Requirements
i. 128 MB RAM
ii. 8 GB Hard Disk
6. APPLICATION DOMAIN
Today, there are hundreds of security solutions available in many market areas, ranging
from Financial Services, and Broadcasting to Government. IDEA is the name of a proven,
secure, and universally applicable block encryption algorithm, which permits effective
protection of transmitted and stored data against unauthorized access by third parties. The
fundamental criteria for the development of Hybrid algorithm were highest security
requirements along with easy hardware and software implementation for fast execution.
This Hybrid algorithm can easily be embedded in any encryption software. Data encryption
can be used to protect data transmission and storage. Typical fields are: Audio and video
data for cable TV, pay TV, video conferencing, distance learning, business TV, VoIP.
There are various fields in which this Hybrid algorithm can be used. These are as follows-
i. Sensitive financial and commercial data
ii. Email via public networks
iii. Transmission links via modem, router or ATM link, GSM technology

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iv. Smart cards
Encryption results in easy detection and recovery of the key. However, since there are 2192
possible keys, this result has no impact on the practical security of the cipher for encryption
provided the encryption keys are chosen at random. IDEA is generally considered to be a
very secure cipher and both the cipher development and its theoretical basis have been
openly and widely discussed so this Hybrid algorithm will result into higher security. IDEA
is a patented and universally applicable block encryption algorithm, which permits the
effective protection of transmitted and stored data against unauthorized access by third
parties. With a key of 128 bits in length, IDEA is far more secure than the widely known
DES based on a 56-bit key. The fundamental criteria for the development of IDEA were
military strength for all security requirements and easy hardware and software
implementation. The algorithm is used worldwide in various banking and industry
applications. They predestine the algorithm for use in a great number of commercial
applications.
7. EXPECTED OUTCOME
This hybrid algorithm has high security of data transmission over the network. This whole
work is focused on how we can increase the security of data transmission. Security is
necessary when we transmit highly sensitive data such as Banking transactions, Military
information and many more.This hybrid algorithm fulfills these criteria up to the mark.
This work results into more secure transmission of data comparatively DES, IDEA and
AES data encryption algorithms.

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8. FUTURE SCOPE
This proposed hybrid algorithm can be made much more powerful and secure by increasing
the number of iterations in the encryption algorithm to suit the level of security required.
An inverse policy of reducing the number of iterations for lower security can also be
employed. We can also go for combining another algorithm that will encrypt data given by
the IDEA algorithm. This inclusion of third algorithm will increase the security but there
are two phase of a coin. As a result Security will increase but time that is taken to convert
the plain text into final cipher text will be greater than previous hybrid algorithm. So it is
the demand of application in which you are going to use security algorithm which factor is
important time or security. We must play a fair role between time taken by the algorithm
and level of security, both must be reasonable.
References
[1] Sombir Singh, Sunil k. Maakar, Dr. Sudesh Kumar “Enhancing the Security of
DES Algorithm Using Transposition Cryptography Techniques”,IJARCSSE,
Volume 3, Issue 6, pp 464-470, June 2013.
[2] Nick Hoffman “A Simplified IDEA Algorithm” Department of Mathematics,
Northern Kentucky University pp 1-5, 2007.
[3] Meier, W., On the Security of the IDEA block cipher, Advances in Cryptology.
[4] Atul Kahate “Cryptography and Network Security” second edition
[5] Shaaban Sahmoud, Wisam Elmasry and Shadi Abdulfa “Enhancement the
security of AES againt modern attacks by using variable key block cipher”,

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International Arab journal of e-technology, vol. 3, No. 1, January 2013
[6] Vishwa Gupta, Gajendra singh, Ravindra Gupta “ Advance cryptography
algorithm for improving data security”, IJARCSSE Volume 2, Issue 1, January
2012
[7] Data Encryption Standard (DES), Federal Information processing standards,
Publication 46-3, 1999 October 25
[8] Advanced Encryption Standard, National Institute of Standards and Technology
(US), URL:http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
[9] William Stallings:”Cryptography and network security:Principles and
Practices”.
[10] Advanced Encryption Standard, [online], Available:
URL:http://en.wikip/Advanced_Encryption_Standard
[11] Wang Tianfu, K. Ramesh Babu “Design Of A Hybrid Cryptographic Algorithm
IJCSCN vol 2(2),277-283

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