# Cryptography Questions and Answers – Public Keys and X.509 Certificates-III

This set of Cryptography Problems focuses on “Public Keys and X.509 Certificates”.

1. How many handshake rounds are required in the Public-Key Distribution Scenario?
a) 7
b) 5
c) 3
d) 4

Explanation: A total of seven messages are required in the Public-Key distribution scenario.

2. A total of seven messages are required in the Public-Key distribution scenario. However, the initial five messages need to be used only infrequently because both A and B can save the other’s public key for future – a technique known as ____
a) time stamping
b) polling
c) caching
d) squeezing

Explanation: This technique is known as caching.

3. X.509 certificate recommends which cryptographic algorithm?
a) RSA
b) DES
c) AES
d) Rabin

Explanation: RSA is the recommended cryptographic algorithm for X.509 certificates.

4. The issuer unique identifier of the X.509 certificates was added in which version?
a) 1
b) 2
c) 3
d) 4

Explanation: The issuer unique identifier was added in the 2nd version.

5. The period of validity consists of the date on which the certificate expires.
a) True
b) False

Explanation: The Period of validity consists of 2 dates: the first and last date on which the certificate is valid.
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6. Certificate extensions fall into 3 categories. Which one of the following is not a Certificate extensions category?
a) Subject and Issuer attributes
b) Key and Policy information
c) Certification path constraints
d) All of the above are Certificate extensions categories

Explanation: Subject and Issuer attributes, Key and Policy information and Certification path constraints are the three categories of Certificate extensions.

7. What does the above figure represent?

a) Hierarchical in X.509
b) IPsec connectivity
d) None of the mentioned

Explanation: The figure is a representation of Hierarchy in X.509.

8. How many functions are involved in the PKIX architectural model?
a) 3
b) 5
c) 6
d) 7

Explanation: The 7 functions are: Registration, Initialization, Certification, Key pair recovery, Key pair update, Revocation request and Cross certification.

9. CMP stands for
a) cipher message protocol
b) cipher management protocol
c) certificate message protocol
d) none of the mentioned

Explanation: CMP stands for certificate management protocol.

10. CMS stands for
a) cipher message syntax
b) certificate message session
c) cryptographic message syntax
d) none of the mentioned

Explanation: CMS stands for cryptographic message syntax.

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