Currently more and more digital certificates are used by agencies and individuals. Usage is also increasingly diverse, such as data encryption, client and server authentication, single-sign-on, and so forth. But with more and more use of digital certificates that can not be checked for validity has been encouraging the owners and creators of data security experts to create a new system called Public Key Infrastructure. Where is the organization that issued a digital certificate has a belief (trust) from other organizations that issue digital certificates and other organizations that also use digital certificates for client authentication. Notably, currently the organizations that use internet services for electronic transactions with their clients being the victim subjects and objects caused by the weakness of the authentication system. In this thesis the author will only restrict the use of digital certificates as a method of client authentication on the website. This thesis is based on the study of the website application implementation by implementing the use of digital certificates for client authentication using Public Key Infrastructure schemes. With this application, the authentication system is expected to filter the client correctly so that valuable information in the website will be maintained and can not easily be accessed by other users who are not eligible.