Digital certificates have a lot of data within them, and you should have a good understanding of what they contain, especially if you plan to take the SY0-501 version or the SY0-401 version of the Security+ exam.
As an example, see if you can answer this sample Security+ question I recently added to the Extras SY0-501 test banks on the gcgapremium.com site.
Q. You are examining a certificate received from a web server used for secure transport encryption. Which of the following items will you be able to see in the certificate? (Choose TWO.)
A. The server’s private key
B. The CAs public key
C. The OID
D. The server’s public key
E. The CSR
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.
Viewing a Digital Certificate
One easy way to see what is in a certificate is to view one. You can use the following steps to view a certificate using Google Chrome.
- Go to https:/gcgapremium.com.
You’ll see a lock icon and the word Secure to the left of the URL. - Click on the word Secure and select Certificate.
You’ll see the certificate open with the General tab selected.
General Tab of the Digital Certificate
The following graphic shows the General tab of a certificate. Notice that this tab shows the purposes of the certificate.
While it doesn’t say it, the certificate is also used to create secure Hypertext Transfer Protocol Secure (HTTPS) sessions with Transport Layer Security (TLS).
The third bullet is a cryptic set of numbers separated by dots (2.23.140.1.2.1). This is the object identifier (OID) for the certificate and provides information on the certificate using the OID format. The 2.23.140.1.2.1 OID indicates it is a domain validated certificate. A domain validated certificate is a server security certificate. It provides assurances that the certificate has been validated to be used with a specific server.
This tab also shows that the certificate was issued to www.gcgapremium.com, the certificate authority (CA) that issued the certificate, and the validity dates.
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Details Tab of the Digital Certificate
The Details tab of the certificate has the most information.
It identifies the version (V3), various algorithms used by the certificate, who issued it, validity dates, and more. The following graphic shows the Details tab with the public key selected.
This public key is distributed with the certificate and matches the private key held on the server. The private key is always kept private and never shared. This public/private pair is used for asymmetric encryption.
Certification Path Tab of the Digital Certificate
The Certification Path tab (shown in the following graphic) of the certificate shows the certification path or trust chain of the certificate.
GlobalSign Root CA – R3 is the root CA. The root CA issues certificates to child CAs (and in some cases intermediate CAs).
In the trust chain shown in the graphic, the root CA issued a certificate to GlobalSign Domain Validation CA – SHA256 – G2. This child CA issues certificates used by others on the Internet, including the site located on the gcgapremium.com server.
Your computer decides to trust this certificate if it trusts the root CA.
Windows systems have a Trusted Root Certification Authority Store with certificates from multiple CAs. The following graphic shows that this system trusts the GlobalSign Root CA. Because it trusts the root CA, it trusts all certificates issued or used by systems in the certification trust path.
The child CA issues certificates for routine use, such as the certificate for www.gcgapremium.com.
Q. You are examining a certificate received from a web server used for secure transport encryption. Which of the following items will you be able to see in the certificate. (Choose TWO.)
A. The server’s private key
B. The CAs public key
C. The OID
D. The server’s public key
E. The CSR
C and D are correct. The object identifier (OID) is a dot-separated series of numbers such as 2.23.140.1.2.1. It is viewable on the General tab of the certificate. The server’s public key is also viewable in the certificate on the Details tab of the certificate.
A server’s private key is always kept private.
The Certification Path tab of the certificate shows the certificate authority (CA) that issued the certificate, but not the CAs public key.
A certificate signing request (CSR) is used to request a certificate, but it is not contained in the issued certificate.
See Chapter 10 of the CompTIA Security+ Get Certified Get Ahead: SY0-501 Study Guide for more information on certificates. The SY0-401 Study Guide also covers certificates in Chapter 10.
SY0-501 objective 6.4 Given a scenario, implement public key infrastructure.
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Certificate, Certificate Revocation List, and Certificate Authority
