E-commerce means buying and selling goods and services across the Internet. Secured communication in e-commerce, across unsecured medium, such as the Internet, represents one of the major components in a domain of providing necessary security- critical demands, so the flow of information could go in a secure way. The Internet, as a global computer network must provide five major security services: confidentiality, data integrity, authentication, availability, and non-repudiation of information. Without guaranteeing aformentioned security goals, risks may be very high in e-commerce systems. A possible way to reduce these risks is to use digital certificates. Digital certificates provide a means of proving identity in electronic transactions, and from the point of view of computer communication they are irreplacable, but nevertheless they provide a good mechanism for implementing the major part of this security goal, and therefore, their usage in e-commerce is the major topic of this paper.