All of the following can be done in Skype EXCEPT ________

Rhapsody's service, provided by RealNetworks, is an example of a(n):

A) instant messenger service B) online music service C) junk e-mail filtering service D) e-mail service provider

A __________ consists of a public key, an identifier of the key owner, and the whole block signed by a trusted third party and can be used by participants to exchange keys without contacting a public key authority in a way that is as reliable as if the keys were obtained directly from a public key authority.

Fill in the blank(s) with the appropriate word(s).