Application Identifier (AID) identifies an application (and certain kinds of files in card file systems) in a smart card or Java Card in accordance with ISO/IEC 7816-5. The Java Card platform uses the AID data format to identify applet and packages. AIDs are administered by the ISO (International Standards Organization). Part of the AID may be registered nationally or internationally, in which case it is reserved for the registered application and is unique worldwide. An AID consists of two data elements: a registered identifier (RID) and a proprietary identifier (PIX).
AIDs are also used in the security policies applets. AIDs are related to the selection mechanisms, packages’ AIDs are used in the enforcement of the firewall. Note: although they serve different purposes, they share the same name space.