The Common Access Card (CAC) is a United States Department of Defense (DoD) smart card, used for email signing, authentication, and access to DoD computers and networks.
The Common Access Card (CAC) is the standard identification for active-duty military personnel, Selected Reserve, DoD civilian employees, and eligible contractor personnel. It is a smart card that can be used for PKI and PIV purposes. In addition it has a 2D bar code for additional identification.