The National Institute of Standard and Technology (NIST)
approved Rijndael algorithm as a standard for Advanced Encryption
Standard (AES) in October 2000. AES is nowadays used extensively
in many network and multimedia applications to protect electronic
data for security issues. In this paper, two architectures
are proposed: one of which reduces the required hardware
requirement, while the second achieves high-speed performance.
The first architecture uses a feedback structure for key
generation. The second architecture uses a memory for key
storage and has a structure of RCON and key expansion unit
that is different from LUT structure. Using VirtexE, two
different key expansion units of both architectures have
been designed and implemented on xcv300e-7bg432 FPGA. For
the first, memory usage is 88388 K bytes, minimum delay
is 11.02 ns (x10) and throughput is 11.17 M bit/sec, while
for the second architecture, the memory usage, minimum delay
and throughput are 99844 K bytes, 9.322 ns and 1.248 G bit/sec
respectively.
Transmission and storage of important data are rapidly
growing in network environments. Along with it grows the
need for efficient and fast data encryption. Cryptography
consists of some mathematical techniques so as to secure
data transmission. In earlier times intelligence agents,
military leaders, and some diplomats used encryption for
the purpose of secrecy in important communications, but
now these are also used for public commercial use. Software
implementations of cryptographic algorithms cannot provide
the necessary performance when large amounts of data have
to be moved with a very high speed that can reach the Gbps
range. Therefore, hardware implementations have to be considered
for these applications, either in ASIC or FPGA forms.
Data Encryption Standard (DES) was the first attempt to
produce high quality government sanctioned encryption algorithm;
then came Triple DES; and finally National Institute of
Standard and Technology (NIST) announced the AES, developed
by Joan Daemen and Vincent Rijmen in order to replace the
aging DES. AES standards have defined some mathematical
steps that are to be followed as an algorithm. Data in its
original form is given as input known as plaintext, and
after performing encryption steps, the result is cipher
text. The cipher text has all the information of plaintext,
but is not in human or computer readable form and the information
can be recovered only after proper decryption. The encrypting
procedure is varied depending on the key, which changes
the detailed operation of the algorithm. Key is essential
for encrypting and decrypting a cipher. The application
of AES algorithm can be found in smart cards, mobile phones,
WWW servers, Automated Teller Machines (ATMs) and digital
video recorders [1, 2, 8, 9].
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