Digital Certificates

Question 1

What is a digitally-signed electronic document that binds a public key with a user’s identity?

Answer 1

Digital certificate

Question 2

When referring to a “user”, what does that entail in regards to digital certificates?

Answer 2

A user can be a server, a real person, a workstation, or another device.

Question 3

What standard is used for digital certificates?

Answer 3

X.509

It contains the owner/users information, and the certificate authorities information. Certificates are signed by a trusted certificate authority or in some cases, self signed.

Question 4

What is contained in a digital certificate?

Answer 4

Owner or user information:
Name, organization, or public key

Certificate Authority information:
Name
Digital signature
CA serial number
Issue date
Expiration date

Question 5

How do you obtain a digital certificate?

Answer 5

You have to purchase it from a certificate authority

Question 6

What is a wildcard certificate?

Answer 6

A certificate that allows the subdomains to use the same public key certificate.

Question 7

Can you use a digital certificate from one of your websites for another one of your websites?

How?

Answer 7

Yes, the certificate must specify the additional domains and IP addresses via the Subject Alternative Name (SAN)

Note: A domain is the name of a website

Question 8

What is the difference between a single sided vs a dual sided certificate?

Answer 8

Single-sided only requires the server to be validated.

Dual-sided requires both the server and user to be validated.

Note: The server identifies itself to the users web browser using the servers digital certificate. In dual-sided the user also validates itself to the server. Dual-sided is usually only used in high-security environments.

Question 9

How are digital certificates validated?

Answer 9

They are validated using a chain of trust

Question 10

What muse happen with a certificate before it can be used?

Answer 10

It must be encoded using X.690 standard. X.690 uses BER, CER, and DER for encoding.

Question 11

What is BER?

Answer 11

The Basic Encoding Rules. The original encoding rules for digital certificates.

Note: This means what type of encoding types can be used for a certificates.

Question 12

What is CER?

Answer 12

The Canonical Encoding Rules. A restricted version of BER that only allow one type of encoding.

Question 13

What is DER?

Answer 13

Distinguished Encoding Rules. A restricted version of BER. It restricts length, character strings, and how elements of digital certificates are stored in X.509.

This is the most common used encoding for X.509 certificates.

Question 14

What are the file extensions for digital certificates?

Answer 14

.pem
.cer
.crt
.key
.p12
.pfx
.p7b

Note: If you get a question regarding these on the exam, its a question related to PKI.