Stand-alone certification authorities

You can install Certificate Services to create a stand-alone certification authority (CA). Stand-alone CAs can issue certificates for purposes such as digital signatures, secure e-mail using S/MIME (Secure Multipurpose Internet Mail Extensions), and authentication to a secure Web server using Secure Sockets Layer (SSL) or Transport Layer Security (TLS).

A stand-alone CA has the following characteristics:

• Unlike an enterprise CA, a stand-alone CA does not require the use of the Active Directory directory service. Stand-alone CAs are primarily intended to be used as Trusted Offline Root CAs in a CA hierarchy or when extranets and the Internet are involved. Additionally, if you want to use a custom policy module for a CA, you would first install a stand-alone CA and then replace the stand-alone policy module with your custom policy module.
• When submitting a certificate request to a stand-alone CA, a certificate requester must explicitly supply all identifying information about themselves and the type of certificate that is wanted in the certificate request. (This does not need to be done when submitting a request to an enterprise CA, since the enterprise user's information is already in Active Directory and the certificate type is described by a certificate template). The authentication information for requests is obtained from the local computer's Security Accounts Manager database.
• By default, all certificate requests sent to the stand-alone CA are set to Pending until the administrator of the stand-alone CA verifies the identity of the requester and approves the request. This is done for security reasons, because the certificate requester's credentials are not verified by the stand-alone CA.
• Certificate templates are not used.
• No certificates can be issued for logging on to a Windows Server 2003 family domain using smart cards, but other types of certificates can be issued and stored on a smart card.
• The administrator has to explicitly distribute the stand-alone CA's certificate to the domain user's trusted root store or users must perform that task themselves.

• If a member of the Domain Administrators group or an administrator with write access to Active Directory, installs a stand-alone root CA, it is automatically added to the Trusted Root Certification Authorities certificate store for all users and computers in the domain. For this reason, if you install a stand-alone root CA in an Active Directory domain, you should not change the default action of the CA upon receiving certificate requests (which marks requests as Pending). Otherwise, you will have a trusted root CA that automatically issues certificates without verifying the identity of the certificate requester.

• If a stand-alone CA is installed by a member of the Domain Administrators group of the parent domain of a tree in the enterprise, or by an administrator with write access to Active Directory, then the stand-alone CA will publish its CA certificate and the certificate revocation list (CRL) to Active Directory.

For more information, compare Enterprise certification authorities. For general information about CAs, see Certification authorities.