Directory Server uses the following types of certificate:
Client SSL certificates are used to identify clients to servers via SSL (client authentication). Typically, the identity of the client is assumed to be the same as the identity of a human being, such as an employee in an enterprise. Client SSL certificates can also be used for form signing and as part of a single sign-on solution.
For example, a bank gives a customer a client SSL certificate that allows the bank’s servers to identify that customer and authorize access to the customer’s accounts. A company might give a new employee a client SSL certificate that allows the company’s servers to identify that employee and authorize access to the company’s servers.
Server SSL certificates are used to identify servers to clients via SSL (server authentication). Server authentication may be used with or without client authentication. Server authentication is a requirement for an encrypted SSL session.
For example, internet sites that engage in electronic commerce usually support certificate-based server authentication, at a minimum, to establish an encrypted SSL session and to assure customers that they are dealing with a web site identified with a particular company. The encrypted SSL session ensures that personal information sent over the network, such as credit card numbers, cannot easily be intercepted.
S/MIME certificates are used for signed and encrypted email. As with client SSL certificates, the identity of the client is typically assumed to be the same as the identity of a human being, such as an employee in an enterprise. A single certificate may be used as both an S/MIME certificate and an SSL certificate. S/MIME certificates can also be used for form signing and as part of a single sign-on solution.
For example, a company deploys combined S/MIME and SSL certificates solely for the purpose of authenticating employee identities, thus permitting signed email and client SSL authentication but not encrypted email. Another company issues S/MIME certificates solely for the purpose of both signing and encrypting email that deals with sensitive financial or legal matters.
For example, a software company signs software distributed over the Internet to provide users with some assurance that the software is a legitimate product of that company. Using certificates and digital signatures in this manner can also make it possible for users to identify and control the kind of access downloaded software has to their computers.
CA certificates are used to identify CAs. Client and server software use CA certificates to determine what other certificates can be trusted.
For example, the CA certificates stored in client software determine what other certificates that client can authenticate. An administrator can implement some aspects of corporate security policies by controlling the CA certificates stored in each user’s client.