Certificates are essential for using asymmetric public-private keys |
RSA set up VeriSign company which offers web certificates for individuals, servers and software publishers |
There are many other authorities |
See http://digitalid.verisign.com/info_ctr.htm for a good description of certificates both in general and for Verisign services (http://www.verisign.com) |
Individual certificates are for use in Web browsers and for secure web mail(S/MIME) such as that offered by Netscape |
There is no agreed format for certificates but X.509 v3 certificate is common (PEM extends this) |