<
communications, security> An
attachment to an {electronic
mail} message used for security purposes, e.g. to verify that
a user sending a message is who he or she claims to be, and to
provide the receiver with the means to encode a reply.
An individual wishing to send an encrypted message applies for
a digital
certificate from a
certificate authority (CA).
The CA issues an encrypted digital
certificate containing the
applicant's
public key and a variety of other identification
information. The CA makes its own public key readily
available on the
Internet.
The recipient of an encrypted message uses the CA's public key
to decode the digital
certificate attached to the message,
verifies it as issued by the CA and then obtains the sender's
public key and identification information held within the
certificate.
(2006-05-27)