Public Key Infrastructure (PKI) in Cybersecurity - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a Certificate Authority (CA) in PKI?

In Public Key Infrastructure, what main role does a Certificate Authority (CA) serve?

A It issues digital certificates that verify the ownership of public keys.

B It encrypts all data transmitted over a network.

C It generates symmetric keys for secure communication.

D It stores private keys securely for all users.

💡 Hint

Think about who confirms that a public key belongs to a specific user or entity.

A Certificate Authority (CA) is trusted to issue digital certificates that prove a public key belongs to a particular entity. This helps others trust the key when communicating securely.

📋 Factual

intermediate

Which component in PKI holds the private key that must remain secret?

In Public Key Infrastructure, which part is responsible for keeping the private key confidential?

A The Certificate Authority (CA)

B The End User or Entity

C The Registration Authority (RA)

D The Public Directory

💡 Hint

Consider who actually owns the key pair and uses the private key to decrypt or sign data.

The end user or entity owns the private key and must keep it secret to maintain security. The CA issues certificates but does not hold private keys for users.

🔍 Analysis

advanced

What happens if a private key in PKI is compromised?

Analyze the consequences if an attacker gains access to a user's private key in a PKI system.

A The attacker can impersonate the user and decrypt messages meant for them.

B The attacker can only view public information but cannot decrypt messages.

C The attacker can revoke the user's digital certificate immediately.

D The attacker can generate new public keys for the user.

💡 Hint

Think about what private keys are used for in encryption and authentication.

If a private key is compromised, an attacker can decrypt confidential messages and impersonate the user by signing data as if they were the owner.

❓ Comparison

advanced

How does a Registration Authority (RA) differ from a Certificate Authority (CA) in PKI?

Compare the roles of a Registration Authority and a Certificate Authority in Public Key Infrastructure.

A RA encrypts data; CA decrypts data.

B RA issues certificates; CA stores private keys securely.

C RA verifies user identity before certificate issuance; CA issues the certificates.

D RA manages public keys; CA manages private keys.

💡 Hint

Consider which entity checks identity and which one actually creates the certificate.

The Registration Authority verifies the identity of users requesting certificates. The Certificate Authority then issues the digital certificates based on that verification.

❓ Reasoning

expert

Why is a Certificate Revocation List (CRL) important in PKI?

Explain the purpose of a Certificate Revocation List in Public Key Infrastructure and its impact on security.

A It stores all valid certificates issued by the CA.

B It encrypts all certificates to protect them from tampering.

C It contains private keys that have been compromised.

D It lists certificates that are no longer trustworthy, preventing their use.

💡 Hint

Think about what happens when a certificate should no longer be trusted.

A Certificate Revocation List (CRL) is a list maintained by the CA that contains certificates that have been revoked before their expiration. This helps systems avoid trusting compromised or invalid certificates.