A Polygraphic, Polyalphabetic Cryptosystem with Public Key and Private Key Encryption

Cryptosystems may be classified as either public key or private key. The system developed in this paper combines the protocols of these two types of cryptography. Techniques and characteristics of previously established cryptosystems are employed as well to produce a three-pass system that is more secure than these earlier systems. Each transmission in the correspondence protocol is at least triply encrypted. The system is also both polygraphic and polyalphabetic in nature. Furthermore, a digital signature enhances the system security by enabling the recipient of an encrypted message to authenticate the identity of the sender. Finally, a greater computational efficiency is achieved than exists in similar previously established systems due to recent results in number theory.