Understanding Public-Key Infrastructure: Concepts, Standards, and Deployment Considerations

Symmetric Versus Asymmetric Ciphers

For as long as humans have communicated, there has been a desire to keep some communications confidential (that is, "hidden") from unintended recipients. Over thousands of years, countless methods for hiding data have been devised. One class of methods attempts to transform the words, letters, or bits to be communicated into something that looks like gibberish rather than a meaningful message. The intended recipient must be able to transform the gibberish back to its original form (in order to read the sender's message), but any other recipient—such as an eavesdropper—should be able to recover nothing more meaningful than the transmitted gibberish.

Two categories of mechanisms exist for performing the transformation ...