A digital certificate.
Digital certificates are issued by commercial certification authorities, such as VeriSign, Inc., who do background checks to verify that the writers or producers of macros (known as publishers) are reputable. You'll find out in the practice session how to check a certificate.
Although it's also possible to "self-certify," self certificates are not considered "trusted." However, they can be handy for internal use.
For more information about creating digital certificates, see Microsoft Help for your Office product or the articles listed in the Quick Reference Card.
Digital certificates have an expiration date, or can get revoked. You can set up revocation checking in Microsoft® Internet Explorer 3.0 or later.
A digital certificate is used to sign macros, creating a digital signature on the macro. A digital certificate can be used many times to create many digital signatures.
Note Although digital certificates can be used with documents and e-mail messages, as well as with macros, they are not used in the same way. For more information about signing documents, see the Quick Reference Card.