Citation
Mohd Ali, Fakariah Hani
(2004)
A faster version of Rijndael Cryptograpic algorithm using cyclic shift and bitwise operations.
Masters thesis, Universiti Putra Malaysia.
Abstract
Doing arithmetic in finite field is the key part to the implementation of
communication and coding system including the newly developed Rijndael the
Advanced Encryption Standard (AES). This encryption standard uses
KeyExpansion, ByteSub, Mixcolumn and Shiftrow functions which consists of
XOR, inverse, multiplying and swap modules. Among them, inverse and
multiplier are the most complex modules with longer delay. These modules are
included in the Mixcolumn function. From the proposal of AES, the
Mixcolumn function was suggested to solve the problem of delay by using
look-up tables. This function can be integrated into a bigger table to replace the
calculations of inverse and multiply operations, if it provides enough memory.
In fact, too many tables are needed for various irreducible polynomials that this
system is not flexible and expandable. The area for lookup tables becomes huge when multiple round units are implemented. This research proposes the use of
cyclic shift and bit wise XOR operation as new approach to replace the lookup
table. The principle benefit of using this new approach over the transform from
Rijndael block cipher is speed. This new approach has shown the excellent
result, which faster then Rijndael. The new approach algorithm speed
increment has consistently increased in between 18% to 22% microsecond for
encryption and 30% to 34% for decryption compared to Rijndael algorithm.
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