Asymmetric-Key Cryptography

An Encryption technique that uses a Public Key and a Private Key, either of which can be used to encrypt or decrypt data. Asymmetric-Key Cryptography can be used in the following ways:

Scenario 1: The intention is to ensure only Andy can read messages from Bertha and Charlie, since they trust him. Bertha and Charlie each use a Public Key (which is known to everyone) to encrypt their messages before sending them to Andy. Andy uses a Private Key (which is known only to himself) to decrypt the messages. Bertha and Charlie are assured that their messages are secured, since only the Private Key can decrypt their messages, and only Andy holds the Private Key.

Scenario 2: The intention is to ensure only Andy can send messages to Bertha and Charlie, since they trust him. This time, Andy uses the Private Key to encrypt his messages before sending them to Bertha and Charlie. Bertha and Charlie use the Public Key to decrypt the messages. Bertha and Charlie are assured that it is Andy who is the sender, since only the Private Key can encrypt such messages, and only Andy holds the Private Key.

Asymmetric-Key Cryptography is also known as Public-Key Cryptography. Contrast this technique with Symmetric-Key Cryptography, in which the same key is used to both encrypt and decrypt data.
And you thought your anti-virus software was complicated …