Once an international public key infrastructure is established a local bank certificate issued to a customer in Bangkok, may be recognized in Los Angeles by any merchant. Income tax returns can be sent electronically signed with digital signatures. Secure electronic commerce of all kinds will be possible once the use of digital signatures with certificates becomes integrated into a public key infrastructure. Another area where digital signatures are beginning to play a critical role is in verification of the integrity of software. Software is increasingly being transmitted over networks and loaded into remote computers.
Software corrupted by errors or an intentionally embedded virus is a major concern.
On the Internet, downloading of software is becoming widely used, especially with JAVA applets loaded onto client computers from Web pages. Digital signatures on software will allow a user to authenticate the author or the software and verify that it has not been altered since it was signed. Use of such digital signatures will again require certificates issued by a certification authority. Within a few years there will be hundreds of millions of people using the Internet. Public Key digital signatures based systems are the only way to secure electronic commerce on the scale of the Internet.