الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Parametric public key cryptosystem is a modification of the usual public key cryptosystem. I n the parametric public key cryptosystem, an additional parameter is passed to the encryption and decryption algorithms. There are several ways to choose how to integrate this parameter into the scheme. We chose a modification of the RSA scheme, in which a new group whose operation requires a parameter a is usedThis operation is xoy = axy+x+y
The new scheme has some interesting properties. One of them is that
given a message parameter pair (a,m), we can forge further encryptions on another message with a different parameter (a’,m’). This property proved helpful when studying the different applications for the scheme. Four applications are introduced for the new scheme. Two of them are known applications that are now being solved in a different way (Chameleon signatures, and probabilistic encryption). We show that the use of paramdric public key cryptosystem allows for simpler and more
time erticient solution for those problems.
The other two application are will validation and signatures in banks. Final1y, analysis is done for the system. Possible attacks are discussed, and a comparison is made between the parametric and non-parametric
publil: key cryptosystel11.