Abstract: This invention concerns an optical storage medium which stores a public key infrastructure(PKI)-based private key and a digital certificate for certificate for certification and security used in electronic commerce, and a method and system for issuing the private key and digital certificate, as well as a method of using such an optical storage medium and system. The optical storage medium, such as a compact disk or digital video disk, provides for a digital signature and may be used in conjunction with a memorized password by the user. By providing an optical storage medium capable of storing large amounts of data, the user can employ the private key and digital certificate even though he or she is not familiar with a computer.