CompTIA Security+ Question E-66

Which of the following types of trust models is used by a PKI?

A. Transitive
B. Open source
C. Decentralized
D. Centralized

Answer: D

Explanation:
PKI uses a centralized trust model. In a simple PKI a single centralized certification authority (CA). In a hierarchical trust model the root CA is the center of the model, with subordinate CAs lower in the hierarchy. Note: A public key infrastructure (PKI) is a set of hardware, software, people, policies, and

procedures needed to create, manage, distribute, use, store, and revoke digital certificates. A trust Model is collection of rules that informs application on how to decide the legitimacy of a Digital Certificate.

CompTIA Security+ Question D-28

In order to use a two-way trust model the security administrator MUST implement which of the following?

A. DAC
B. PKI
C. HTTPS
D. TPM

Answer: B

Explanation:
PKI is a high level concept. Within a PKI you use a trust model to set up trust between Certification Authorities (CAs). A public key infrastructure (PKI) is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates.

CompTIA Security+ Question B-84

A network administrator is looking for a way to automatically update company browsers so they import a list of root certificates from an online source. This online source will then be responsible for tracking which certificates are to be trusted or not trusted. Which of the following BEST describes the service that should be implemented to meet these requirements?

A. Trust model
B. Key escrow
C. OCSP
D. PKI

Answer: A

Explanation:
In this scenario we can put a CA in the local network and use an online CA as root CA in a hierarchical trust model. A trust Model is collection of rules that informs application on how to decide the legitimacy of a Digital Certificate. In a hierarchical trust model, also known as a tree, a root CA at the top provides all of the information. The intermediate CAs are next in the hierarchy, and they trust only information provided by the root CA. The root CA also trusts intermediate CAs that are in their level in the hierarchy and none that aren’t. This arrangement allows a high level of control at all levels of the hierarchical tree.

CompTIA Security+ Question A-66

Some customers have reported receiving an untrusted certificate warning when visiting the company’s website. The administrator ensures that the certificate is not expired and that customers have trusted the original issuer of the certificate. Which of the following could be causing the problem?

A. The intermediate CA certificates were not installed on the server.
B. The certificate is not the correct type for a virtual server.
C. The encryption key used in the certificate is too short.
D. The client’s browser is trying to negotiate SSL instead of TLS.

Answer: A

Explanation:
In a hierarchical trust model, also known as a tree, a root CA at the top provides all of the information. The intermediate CAs are next in the hierarchy, and they trust only information provided by the root CA. The root CA also trusts intermediate CAs that are in their level in the hierarchy and none that aren’t.