Secret Encryption with Public Keys

For centuries people have wished to communicate with one another while keeping their communications secret from outsiders. In order to accomplish this, the sender of a message must disguise it before sending it. The process of disguising a message is called encryption or enciphment. The receiver, after receiving the encrypted message, must translate it back to its original form. This reverse process is called &cryption or dec;Phmnt. The scheme used to encrypt and decrypt the message is known as an encryption system, cryptosystem, or cipher. Devising a good encryption system is a difficult task, and an encryption system, once devised, is subject to attack by people who wish to crack the system, thereby enabling themselves to decrypt messages or to send their own encrypted messages intended to deceive the original users of the cryptosystem.