Remailers
Allow a person to keep their email address confidential by providing an alternative path through which the message is delivered to its final destination.

Reverse domain name hijacking
Using any intellectual property rights principles in bad faith in an attempt to deprive a registered domain name holder of a domain name. This is usually an attempt by a more formidable entity to take an address away from a less powerful, but otherwise legitimate, owner.

Rights Management Information (RMI)
Information attached to or embodied in digital material identifying the material, its author or the copyright owner and any terms of use.

RSA algorithm
One of the most popular current commercial digital signature mechanisms.