Asymmetric Encryption

Excerpt from http://www.4guysfromrolla.com/articles/021407-1.aspx

In asymmetric encryption two keys are generated per entity, one which is kept private and the other which is publicly known. The interesting and most important attribute of each of the two keys is that: each key undoes the other's operations, and it is computationally infeasible to generate the opposite key given one of the keys. As Figure 2 illustrates, if Bob wants to send a message to Alice, he uses Alice's public key to encrypt the message with. Later, when Alice wants to decrypt the message, she only needs to use her private key to do so. This method ensures that only Alice is able to read the messages encrypted with her public key.