Abstract:
The purpose of this thesis is to give up to date discussion of the principles, techniques
and algorithms of interest in cryptographic practice. We choose to emphasize on the
most practical and applied cryptographic system, El-Gamal scheme.
This thesis discusses modifications we made on El-Gamal scheme, mainly extending
the scheme to work on the second group of units of Zn and the second group of units
of the quotient ring of polynomials over a field with cyclic second group of units.
The arithmetic needed in this new setting is described. Algorithms are given.
Advantages and efficiency of the new method are pointed out. Finally the security of
the new scheme is studied and suggestions for further work are introduced.
