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This section contains procedures for the following subjects:

The CAs on the CTL should be those that issue user certificates that you want 
Cisco Secure ACS to recognize as trustworthy. 

TLS authentications require two elements of trust. The first element of trust is 
when the TLS negotiation establishes end-user trust by validating, through RSA 
signature verifications, that the user is in possession of a keypair signed by a 
certificate. This verifies that the end user is the legitimate keyholder for a given 
digital certificate and corresponding user identification contained in the 
certificate. However, trusting that a user is in possession of a certificate only 
provides a username/keypair binding. The second element of trust is to use a 
third-party signature (usually from a CA) that verifies the information in a 
certificate. This third-party binding is similar to the real world equivalent of the 
U.S. Passport seal on your passport. You trust the passport because you trust the 
preparation and identity checking that the passport office made when creating that 
passport. You trust digital certificates by installing the root certificate CA 
signature in an equivalent way. 

How you edit your CTL determines the type of trust model you have. Many 
employ a restricted trust model wherein very few, privately controlled CAs are 
trusted. This model provides the highest level of security but restricts adaptability 
and expandability. The alternative, an open trust model, allows for more CAs or 
public CAs. This open trust model trades off increased security for greater 
adaptability and expandability.

We recommend that you fully understand the implications of your trust model 
before editing the CTL in Cisco Secure ACS.