The invention provides an information processing system, a portable electronic device, an access apparatus for the portable electronic device, as well as a method of using a memory space. When applied to, for example, a system employing non-contact IC cards, the invention enables one IC card to be used for a plurality of business organizations in common. To this end, an access key is created based on issuer key information managed by a management sector and file key information specific to each business organization, and the created access key is signed to the business organization. A portable electronic device is then accessed using the access key.