a fast and secure rsa public key cryptosystem

Rsa is a well - known public - key cryptosystem . it is the most commonly used and currently most important public - key algorithm which can be used for both encryption and signing . rsa cryptosystem involves exponentiation modulo an integer number n that is the product of two large primes p and q . the security of the system is based on the difficulty of factoring large integers in terms of its key size and the length of the modulus n in bits which is said to be the key size . in this paper , we present a method that increases the speed of rsa cryptosystem . also , an efficient implementation of arithmetic and modular operations are used to increase its speed . the security is also enhanced by using a variable key size space . there exist numerous implementations ( hardware or software ) of rsa cryptosystem , but most of them are restricted in key size . an important improvement achieved in this paper is that the system is designed flexible in terms of key size according to user security .