Design and Implementation of Hybrid Encryption Algorithm

Abstract

In today's world 99% people are more interested in sending and receiving data through the internet and mobile data storage devices. But among those people don't encrypt their data though they know that data contains personal information and the chances of data lose or hacking is very high. Information security has always been important in all aspects of life. It can be all the more important as technology continues to control various operations in our day-today life. Cryptography provides a layer of security in cases, where the medium of transmission is susceptible to interception, by translating a message into a form that cannot be read by an unauthorized third party. The ultimate objective of the research presented in this paper is to develop both AES and Blowfish to be low power, high-throughput, real-time, reliable and extremely secure cryptography algorithm and in addition to making an estimation of both AES and Blowfish more difficult seems impossible.

Full text

Design and Implementation of Hybrid Encryption Algorithm
Ali E. Taki El_Deen
IEEE Senior Member, Alexandria University, Egypt.
A_takieldeen@yahoo.com
Abstract – In today’s world 99% people are more interested in
sending and receiving data through internet and mobile data
storage devices. But among those people don’t encrypt their data
though they know that data contains personal information and
the chances of data lose or hacking is very high. Information
security has always been important in all aspects of life. It can
be all the more important as technology continues to control
various operations in our day-to-day life. Cryptography provides
a layer of security in cases, where the medium of transmission
is susceptible to interception, by translating a message into
a form that cannot be read by an unauthorized third party.
The ultimate objective of the research presented in this paper is
to develop both AES and Blowfish to be low power, high-
throughput, real-time, reliable and extremely secure
cryptography algorithm and in addition to making estimation of
both AES and Blowfish more difficult seems impossible.
Keywords: Blowfish, AES, DES, RSA
TABLE OF CONTENTS
1.INTODUCTION………………………………1
2. THE BLOWFISH ALGORITHM ……………..1
3. 128 - BITS AES ALGORITHM ……………...2
4. AES, DES, RSA, AND BLOWFISH…..……..4
5. STATISTICAL TESTS…………………….….4
6. HYBRID ENCRYPTION ALGORITHM….…….4
7. Contribution of This Paper and Future
Work………………………………….....……5
REFERENCES…………………………………6
BIOGRAPHY…………………………………..6
1. Introduction
Hybrid Encryption Algorithm is a keyed, symmetric
block cipher, designed in 2012. It is a combination of two
known algorithms ( Blowfish & AES 128 ) .
Hybrid Encryption Algorithm takes the
advantages of blowfish algorithm and Advanced-
Encryption-Standard (AES) algorithm makes it harder for
any attacker to try to decrypt the cipher text.
Hybrid Encryption Algorithm requires fast
processing techniques. Hybrid Encryption Algorithm is a
high encryption security.
2. The Blowfish Algorithm
Blowfish has a 64-bit block size and a key length
of anywhere from 32 bits to 448 bits (32-448 bits in steps
of 8 bits; default 128 bits).
It is a 16-round Feistel cipher and uses large key-
dependent S-boxes. It is similar in structure to CAST-128,
which uses fixed S-boxes.
There are two parts here:
 A part that handles the expansion of the key.
 A part that handles the encryption of the data.
The expansion of the key:
Breaking the original key into a set of subkeys.
Specifically, a key of no more than 448 bits is separated
into 4168 bytes. There is a P-array and four 32-bit S-
boxes. The P-array contains 18 32-bit subkeys, while each
S-box contains 256 entries.
The encryption of data:
The encryption of the data: 64-bit input is
denoted with an x, while the P-array is denoted with a Pi
(where i is the iteration).
Figure1 shows the action of Blowfish. Each line
represents 32 bits. The algorithm keeps two subkey
arrays: the 18-entry P-array and four 256-entry S-boxes.
The S-boxes accept 8-bit input and produce 32-
bit output. One entry of the P-array is used every round,
and after the final round, each half of the data block is
XORed with one of the two remaining unused P-entries.
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Fig. 1 Blowfish algorithm
Figure explanation:
 Initialize the P-array and S-boxes.
 XOR P-array with the key bits. For example, P1
XOR (first 32 bits of key), P2 XOR (second 32
bits of key). Use the above method to encrypt
the all-zero string.
 This new output is now P1 and P2.
 Encrypt the new P1 and P2 with the modified
subkeys.
 This new output is now P3 and P4.
 Repeat 521 times in order to calculate new
subkeys for the P-array and the four S boxes.
Fig. 2 Blowfish F function
Advantage of Blowfish:
1. Fast. Blowfish encrypts data on 32-bit microprocessors
at a rate of 26 clock cycles per byte.
2. Compact. Blowfish can run in less than 5K of memory.
3. Simple. Blowfish uses only simple operations: addition,
XORs, and table lookups on 32-bit operands. Its design is
easy to analyze which makes it resistant to
implementation errors [1391].
4. Variably Secure. Blowfish’s key length is variable and
can be as long as 448 bits.
3. 128 - Bits AES Algorithm
Fig. 3 AES flowchart
Figure 3 shows the structure of AES in more
detail. The cipher consists of N rounds, where the number
of rounds depends on the key length: 10 rounds for a 16-
byte key; 12 rounds for a 24-byte key; and 14 rounds for a
32-byte key. The first N – 1 rounds consist of four distinct
transformation functions: SubBytes, ShiftRows,
MixColumns, and AddRoundKey, which are described
subsequently. The final round contains only 3
transformations, and there is a initial single
transformation (AddRoundKey) before the first round,
which can be considered Round 0. Each transformation
takes one or more 4 x 4 matrices as input and produces a
4 x 4 matrix as output. Figure 4 shows that the output of
each round is a 4 x 4 matrix, with the output of the final
round being the ciphertext. Also, the key expansion
function generates N + 1 round keys, each of which is a
distinct 4 x 4 matrix.
Each round key serves as one of the inputs to the
AddRoundKey transformation in each round.
The main 4 functions in AES:
1. SubByte
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2. Shift Row
3. Mix Columns
4. Add Round Key
Fig. 4 The output of each round
Advantage of AES:
1. Advanced Encryption Standard (AES) algorithm works
on the principle of Substitution Permutation network.
2. AES has more elegant mathematical formulas behind
it, and only requires one pass to encrypt data. AES was
designed from the ground up to be fast, unbreakable and
able to support the tiniest computing devices imaginable.
The big differentiators between AES and Triple-DES are
not strength of security, but superior performance and
better use of resources.
3. Advanced Encryption Standard not only assures
security but also improves the performance in a variety of
settings such as smartcards, hardware implementations
etc.
4. AES is federal information processing standard and
there are currently no known non-brute-force direct
attacks against AES.
5. AES is strong enough to be certified for use by the US
government for top secret information.
AES Round:
Fig. 5 AES round
4. Comparison between AES, DES, RSA,
and Blowfish
Key type
Key size
Block
size
AES
Symmetric
128 bits
128 bits,
192 bits,
and 256
bits
DES
Symmetric
64 bits (56
bits are
actually used)
64 bits
RSA
Asymmetric
Not specified
Not
specified
Blowfish
Symmetric
64 bits
From 32
bits to 448
bits
Table 1: Comparison between AES, DES, RSA, Blowfish
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5. Statistical Tests
Let s = s0; s1; s2; ….. ; sn−1 be a binary sequence of
length n. This subsection presents four statistical tests that
are commonly used for determining whether the binary
sequence s possesses some specific characteristics that a
truly random sequence would be likely to exhibit. It is
emphasized that the outcome of each test is not definite,
but rather probabilistic. If a sequence passes all four tests,
there is no guarantee that it was indeed produced by a
random bit generator [19]. These tests are:
 Frequency test (Monobit test).
 Serial test.
 Poker test.
 Run test.
For a significance level of α = 0.05, the threshold
values for freq., serial, poker, and run tests are 3.8415,
5.9915, 14.0671, and 9.4877 respectively [10]. Our tests
results are given in figure 3.
6. Hybrid Encryption Algorithm
NOTE: The following is first idea but we still
developing our algorithm.
Statistical tests of Text Data:
Fig. 6 Tests values
Encryption:
There are four parts to this algorithm:
1. Part that handles the expansion of the key used in
blowfish.
2. Part that handles the expansion of the key used in AES.
3. Part that handles the encryption of the data using
blowfish.
4. Part that handles the encryption of the encrypted data
from blowfish using AES128.
Part 1:
Blowfish key: break the original key into a set of
subkeys. Specifically, a key of no more than 448 bits is
separated into 4168 bytes. There is a P-array and four 32-
bit S-boxes. The P-array contains 18 32-bit subkeys,
while each S-box contains 256 entries.
Part 2:
AES key: expansion of 128 bit only from the key
whish will give 10 partial keys used in the initial round, 9
main rounds and one final round.
Part 3:
Make the encryption of 128 bit from plain text
using blowfish by making encryption to the first 64 bit
then to the second 64 bit.
Part 4:
Take the output of the encrypted 128 bit that
comes from making blowfish twice and make this output
the input plain text to AES algorithm.
Fig. 7 Hybrid Encryption Algorithm
0
10
20
30
40
50
60
70
80
90
Frequency
Test
Serial Test Poker Test Run Test
Values
Statistical Tests
128-Bit-AES
192-Bit-AES
256-Bit-AES
RSA
BlowFish
DES
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Decryption:
1. Part that handles the expansion of the key used in
blowfish.
2. Part that handles the expansion of the key used in AES.
3. Part that handles the decryption using AES128 to the
encrypted data using blowfish.
4. Part that handles the decryption of the data using
blowfish.
In decryption part one and part two are the same
as there is no change in key generation for both blowfish
and AES. For part 3 and 4 we will start with part 4 then
part 3.
Figure 7 describes the main steps of Hybrid
Encryption Algorithm encryption and how it start
normally with the input key from user and make
blowfish encryption two times to get 128 bit encrypted
then we make AES encryption one time to the 128 bit
output from the two times blowfish encryption. using
only the first 128 bit from key as the key may get too
long as we can use up to 448 bit or 576 bit key in
blowfish , then finally we get the 128 bit encrypted .
7. Contribution of This Paper and Future
Work
In this paper, Hybrid Encryption Algorithm has
been introduced. The proposed technique of Hybrid
Encryption Algorithm combines between difficulty of
estimation the original text and verity of using the
different key on blowfish and AES encryption that we
introduce cipher text more difficult for estimation so our
algorithm is at high level of security and we need that to
use it in specific applications like military applications,
hardware and software companies that need security in
their products, banks, networks companies, big websites
that have big databases and mobile networks. Also a
comparison between AES, DES, RSA, and Blowfish encryption
algorithms are discussed. Statistical tests of AES, DES,
RSA, and Blowfish algorithms have been examined.
REFERENCES
[1] William Stallings, Network Security Essentials:
Applications and Standards, Prentice Hall, 4th edition,
2011.
[4] B. Schneier, Speed Comparisons of Block Ciphers
On a Pentium, Retrieved 12:04:58, July 27, 2008 from
http://www.schneier.com/blowfish-speed.html.
[5] B. Schneier, in: Applied Cryptography, second ed.,
John Wiley & Sons, Inc., New York, 1996.
[6] B. Schneier, The Blowfish Encryption Algorithm.
Retrieved July 27, 2008 from
http://www.schneier.com/blowfish.html.
[8] Pieprzyk, J.; Hardjono, T.; and Seberry, J.,
Fundamentals of Computer Security. New York:
Springer-Verlag, 2003.
[13] J. Daemen and V. Rijmen, AES Proposal: Rijndael,
AES Algorithm Submission,September 3, 1999.
[14] A. Lee, NIST Special Publication 800-21, Guideline
for Implementing Cryptographyin the Federal
Government, National Institute of Standards and
Technology,November 1999.
[15] J. Nechvatal, et. al., Report on the Development of
the Advanced Encryption Standard (AES), National
Institute of Standards and Technology, October 2, 2000.
[17] Wenbo Mao, Modern Cryptography: Theory and
Practice: By Hewlett-Packard Company, Publisher:
Prentice Hall PTR, Pub Date: July 25, 2003, ISBN: 0-13-
066943-1.
[7] Avi Kak, “AES: The Advanced Encryption Standard,
Lecture Notes on “Computer and Network Security””,
February, 2013.
Biography
Ali E. Taki El_Deen (IEEE Senior
Member) received the PhD degree in
Electronics and Communications
Engineering in “Encryption and Data
Security in Digital Communication
Systems”. He has a lot of publications in
various international journalsand conferences. His
current research interests are in multimedia processing,
wireless communication systems, Microcontroller and
Field Programmable Gate Array (FPGA) applications.
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