This set of Cryptography Multiple Choice Questions & Answers (MCQs) focuses on “Public Keys and X.509 Certificates – 2”.
1. Extensions were added in which version?
Explanation: Extensions to the X.509 certificates were added in version 3.
2. The subject unique identifier of the X.509 certificates was added in which version?
Explanation: The subject unique identifier was added in the 2nd version.
3. Which of the following is not an element/field of the X.509 certificates?
a) Issuer Name
b) Serial Modifier
c) Issuer unique Identifier
Explanation: Serial Modifier is not an element/field of the X.509 certificates.
4. Suppose that A has obtained a certificate from certification authority X1 and B has obtained certificate authority from CA X2. A can use a chain of certificates to obtain B’s public key. In notation of X.509, this chain is represented in the correct order as –
a) X2 X1 X1 B
b) X1 X1 X2 A
c) X1 X2 X2 B
d) X1 X2 X2 A
Explanation: The correct representation would be X1 X2 X2 B.
5. Certificates generated by X that are the certificates of other CAs are Reverse Certificates.
Explanation: The statement is true. Certificates of X generated by other CAs are forward certificates.
6. It is desirable to revoke a certificate before it expires because
a) the user is no longer certified by this CA
b) the CA’s certificate is assumed to be compromised
c) the user’s private key is assumed to be compromised
d) all of the mentioned
Explanation: All of the options are true with regard to revocation of a certificate.
7. CRL stands for
a) Cipher Reusable List
b) Certificate Revocation Language
c) Certificate Revocation List
d) Certificate Resolution Language
Explanation: CRL stands for Certificate Revocation List.
8. Which of the following is not a part of an Extension?
a) Extension Identifier
b) Extension value
c) Criticality Indicator
d) All of the mentioned constitute the Extension
Explanation: Extension Identifier, Extension value and the Criticality Indicator all constitue the Extension header.
9. The criticality indicator indicates whether an extension can be safely ignored.
Explanation: The statement is true.
10. “Conveys any desired X.500 directory attribute values for the subject of this certificate.”
Which Extension among the following does this refer to?
a) Subject alternative name
b) Issuer Alternative name
c) Subject directory attributes
d) None of the mentioned
Explanation: The Subject directory attributes has the function of conveying any desired X.500 directory attribute values for the subject of this certificate.”
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