Without knowing an individuals signing code, it is impossible to produce the correct set of numbers that constitute a valid signature. Documents are signed using an individual s signing code and are subsequently verified using the verification code. However one issue of importance that arises is the question of who exactly owns these codes. What is required is a method to bind these codes to a particular individual. This is achieved through the use of digital certificates.
Digital certificates are electronic equivalents of a passport or identity card.
Just as a passport binds a particular photograph and signature to an individual so a digital certificate binds a particular signing and verification code to the same individual. To know which verification codes belong to which people all we need do is check their digital certificates. Certification Authorities are the organisations that issue digital certificates. Their function is to verify the identity of a particular individual and issue a certificate to that individual. The individual s verification code.