Cryptosystem A cryptosystem is composed of a set (Ee:eEX} consisting of enciphering transformations and the corresponding set (Ee:eeX)={Da:deX) of deciphering transformations.In other words,for eacheK,there erists a unique dK such that Da=E,so that Da(Ee(m))=m for all mM. The keys (e,d)are called a key pair where possibly e=d.A cryptosystem is also called a cipher.Cryptosystem