A vlsi implementation of a resource efficient and secure architecture of a block cipher

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
A VLSI IMPLEMENTATION OF A RESOURCE EFFICIENT AND
SECURE ARCHITECTURE OF A BLOCK CIPHER
Satish Shivaram1
, R.Krishna2
, Vijayaprakash3
, K.V.Prasad4
1
Student, Electronics and Communication, Bangalore Institute of Technology, Karnataka, India.
2
Assistant Professor, Electronics and communication, Bangalore Institute of Technology, Karnataka, India.
3
Professor, Electronics and Communication, Bangalore Institute of Technology, Karnataka , India.
4
Professor and HOD, Electronics and Communication, Bangalore Institute of Technology, Karnataka, India.
Abstract
In today‘s modern life, the protection of data is of major concern in any kind of domian. So the understanding of cryptography
architecture plays a crucial role. Advance encryption system , differential encryption system design of cryptography have few
drawbacks in implementation level of low level designs. In an area concerned and power concerned parameters the above
mentioned algorithms have failed in implementing. The humming bird algorithm uses block cipher which is being used in this
paper for encryption and decryption using 128 bit secure key. Block cipher concentrates on converting the given original data
into cipher text to make the given data more secure over the user. Two different designs of block Cipher algorithms (Throughput
enhanced , Area reduced) are developed and their performance is compared in terms of area occupation using Xilinx ISE design
tool with verilog language. The block cipher designs are implemented using 64 bit secure key and 128 bit secure key. The area
reduced design is of the concern to have this module on the FPGA implementation in the VLSI sector.
Keywords : Cryptography, VLSI, FPGA , Block Cipher.
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1. INTRODUCTION
After the computer invention the need of developing
tools to protect the information (data) stored in the
computer raised. To fulfill this requirements number of
tools designed and developed with the main goal of
protecting information present in the computer from
hackers. These facilities are generally called as computer
security. The development of communication and network
facilities make it possible to share the information between
computers and then the problem of hacking of information
arises from this the concept of network security developed.
Cryptography is a technique that makes information not
readable by unauthorized persons, by the use of encoding
method. Some of the application of cryptography includes
the security of ATM cards, use of passwords in computer
and electronic commerce. Cryptography is derived from
the Greek words ‗kryptos‘(hidden) and ‗graphos‘(written)
respectively. Cryptography involves two processes. These
are encryption and decryption. Encryption converts the
plain text to cipher text. Decryption converts cipher text to
plain text.
The main goal of cryptography is to make our information
confidential. There are various cryptographic algorithms
have been developed. The design of any cryptographic
algorithm requires the focus on three parameter: these are
―security, cost and performance‖. So depending on
particular application one can choose better algorithm
suitable for that application.
Standardized algorithms like AES, DES etc, fails to provide
security in applications such as RFID tag, sensor nodes, and
smart cards. These algorithms demands the support of more
resources, lightweight cryptography can be used as an
alternative for these application, which gives better security
compared to standardized cryptographic algorithms. This
gives motivation for the designer to move towards
lightweight cryptographic algorithms.
Hummingbird cryptography is one of the lightweight
cryptographic algorithms. Design of Hummingbird
cryptography is motivated by the enigma machine . It is
found that it uses small sized block and able to withstand
cryptographic attacks like linear and differential
cryptanalysis.
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Volume: 05 Issue: 08 | Aug-2016, Available @ http://ijret.esatjournals.org 172

In this paper hummingbird cryptographic algorithm is
considered and tries to modify the block cipher used to
reduce the area and enhanced performance without affecting
the security of algorithm.
In this paper block cipher is designed using throughput
enhanced and area reduced architecture. The secure key
used in this paper is 128 bit instead of 64 bit which was used
in previous work. The S-box used here makes use of the
readily available LUT which is shown in the methodology
section. Both encryption and decryption work are carried out
to show the given plain text is secured in high terms with
large number of bits. With the same key used the given plain
text can be obtained making the information more secure.
The area utilization of both throughput enhanced and area
reduced are obtained by synthesis report by using Xilinx
14.6 and are compared. Simulation results are obtained
using ModelSim 10.1 and the waveforms are observed.
The Theoretical backgrounds of cipher block and proposed
architecture will be described in the next two sections. The
simulation results and synthesis report will be discussed
before conclusion.
2. THEORETICAL BACKGROUND
In this section the basic flow chart of through put enhanced
design and area reduced design is incorporated.
In the first step the 16 bit plain text data is mixed with the
128 bit secure key which is subdivided into 8 different 16 bit
secure key. Followed by this step is substitution step where
the S-box plays an important role for both encryption and
decryption. In this paper readily available S-box LUT is
being used instead of representing Boolean expressions.
linear transformation is followed after substitution layer.
After eight times iteration the second round key with
exoring with all odd numbers of key is given to S-box and
linear transform layer. The process is repeated as shown in
fig 1.
The readily available S-box is shown below.
Table 1: S-Boxes given in Hexadecimal format
x 0 1 2 3 4 5 6 7
8 6 5 F 1 C A 9
0 7 E 1 5 B 8 2
2 E F 5 C 1 9 A
0 7 3 4 C 1 A F
x 8 9 A B C D E F
E B 2 4 7 0 D 3
3 A D 6 F C 4 9
B 4 6 8 0 7 3 D
D E 6 B 2 8 9 5
3. PROPOSED ARCHITECTURE
a. Throughput enhanced design:
In this paper, the cipher block is presented by new
expressions. The encryption and decryption block is
designed separately using 128 bit has the new proposed
design. The basic design of throughput enhanced design of
block cipher using 128 bit secure key is as shown in fig 1.
The proposed work goes well with the theoretical
background with flow chart starting with the key mixing
step with the given plain text. Followed by substitution layer
where S- box plays an important role. In this paper we are
using readily available S-box as shown in table 1.
Followed by linear transformation layer which is given by
m^m<<6^m<<10 expression for encryption. These steps are
repeated 8 times with different 16 bit secure key.
K9 is calculated with all the odd numbers of keys exoring
and leads to S-box substitution and linear transformation
and then k10 is calculated with all the even number of keys.
The final 16 bit encrypted data of the given plain text data is
obtained which is further made use in the decryption block
using the same 128 bit secure key.
Fig 1. Block diagram of proposed throughput enhanced
encryption unit
The decryption block using 128 bit secure key is as shown
in fig 2. Here the operation are carried out in a similar
manner as compared to encryption block which is the mirror
operation of it.
________________________________________________________________________________________________________

The only difference is the way the S-box readings are made
which is inverse. In the next inverse linear transform the
expression is given by m^m<<6^m<<10^m<<12. All the
operations are inversed starting from key k10 to k1. The
decrypted data is same as the plain text given and the
procedure followed serves the purpose.
Fig 2. Block diagram of proposed throughput enhanced
decryption unit.
b. area reduced design:
in this paper major proposal is to get area reduction on fpga.
The area reduced design encryption is shown in fig 3.
In this design the number of components are reduced in the
first part of substitution and linear transformation unit. The
eight iterations are reduced with one unit where each key
processing output is stored in a flop and based on the key
select and data select operations are performed and the
synthesis report is been generated and compared with the
throughput enhanced version. We can see the number of 4
input LUTs used is reduced in this design.
Fig 3. Block diagram of proposed area reduced design unit.
Simulation results:
Simulation results are seen using ModelSim 10.1b
________________________________________________________________________________________________________

Fig 4. Waveform of throughput enhanced encryption using 128 bit secure key.
Fig 5. waveform of throughput enhanced decryption unit using 128 bit secure key
________________________________________________________________________________________________________

Fig 6. waveform of area reduced encryption unit using 128 bit secure key.Synthesis report :
Syntesis is done using Xilinx 14.6 version.
Table 2: Device utilization summary
Module Area in LUT
Throughput Oriented 128 252
Area oriented 128 104
Through put base paper 64 132
Area oriented 64 88
CONCLUSION
In this paper , the cipher block named throughput enhanced
and area reduced block ciphers are implemented. Both
encryption and decryption units are developed and
implemented. The round keys are generated and registered
using 128 bit secure key instead of 64 bit key used in the
previous work. The S – box implementation is done using
readily available LUTs instead of Boolean expression which
is time consuming and more number of slices for
implementation.
The simulation and synthesis reports are tabulated . as seen
from the table 2 area reduced design required lesser number
of 4 input LUT compared to throughput enhanced design.
This shows that single module chip area optimization is
observed in greater manner. This is a well balanced
architecture with high performance and low complexity.
This cipher block can also be used in wireless sensor nodes
and smart chips.
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2014.
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A vlsi implementation of a resource efficient and secure architecture of a block cipher

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A vlsi implementation of a resource efficient and secure architecture of a block cipher