Exam CAS-004 topic 1 question 132 discussion

This is a terrible question. None of these tell you if the key has been compromised. The only thing you can do is check CRL or OSCP to see if it's been revoked... but it could be compromised and not been revoked yet.

Why not OSCP? When a client system receives a digital certificate from a server, it can use OCSP to check the status of the certificate and determine whether it is still valid. This allows the client system to verify the authenticity of the certificate and ensure that it has not been compromised or revoked. CRL (Certificate Revocation List) is a list of digital certificates that have been revoked by a certification authority (CA). It can be used to verify the status of a certificate, but it is not a real-time verification method like OCSP.

CRL provides a comprehensive list of all revoked certificates, making it useful for offline checks but may have latency issues. OCSP offers real-time, efficient checks of individual certificate status, making it more suitable for immediate and up-to-date validation.

While CRLs are effective, the process of downloading and checking the entire CRL can be resource-intensive, especially in large-scale deployments. OCSP is a protocol that enables real-time verification of the status of a digital certificate. Instead of relying on periodic downloads of a CRL, OCSP allows the client to query the CA for the revocation status of a specific certificate.

CRL (Certificate Revocation List) is a list of certificates that have been revoked by the certificate authority before their scheduled expiration date. While CRLs are important for certificate management, they are not directly used for checking the compromise of private keys.

I've been back and forth during studying and trying to determine the answer to this question. Both OCSP and CRL are the correct choices and putting myself in the situation, I would check the OCSP and then confirm with the CRL. So I would believe that the CRL is the best reliable source to get the confirmation. OCSP can provide us some great information and I do it all the time to check if domains are spoofed or not during work, but CRL would have the most reliable information

B: A certificate may be revoked or suspended by the owner or by the CA for many reasons. For example, the certificate or its private key may have been compromised, the business could have closed, a user could have left the company, a domain name could have been changed, the certificate could have been misused in some way. CAs must maintain a certificate revocation list (CRL) of all revoked and suspended certificates, which can be distributed throughout the hierarchy.

D: "The CRL method requires the browser to download the list of all the revoked certificates and parse it to look for the certificate serial number. As such, it can take longer to come up with a result than it does to request a single certificate’s revocation status with OCSP. Downloading the CRL also uses more network resources than downloading the response for a single website, so OCSP is less resource intensive." https://sectigostore.com/blog/ocsp-vs-crl-whats-the-difference/

Answer is D, OSCP per Sybex book page 244: "if private key is exposed or another situation arises where the certificate must be revoked, PKI has a way to deal with such situations, that is, when a CRL is used. These list can be checked via the OCSP, an internet protocol used for obtaining the revocation status of an X.509 digital certificate."

OCSP provides the fastest and most realistic way to check if the key is valid. An Analyst checking the entire CRL is unrealistic; at this point of the investigation, it has not been confirmed as compromised. Updating the CRL directly would be a no-brainer if it were confirmed compromised. Source: Verifying each answer against Chat GPT, my experience, other test banks, a written book, and weighing in the discussion from all users to create a 100% accurate guide for myself before I take the exam. (It isn't easy because of the time needed, but it is doing my diligence)

D. OCSP Cons of CRL below Generally, the CRL returned contains thousands of line, which can cause a considerable effect on the network and client performance. Typically the publishing of a new CRL is very slow, which can leave the client open to attacks. If for some reason a client is unable to download the CRL, it’ll default to trusting the certificate. https://www.encryptionconsulting.com/ocsp-vs-crl/

OCSP is a real-time method for checking the revocation status of a certificate. It allows the analyst to query a certificate authority (CA) in real-time. CRL is an indirect connection between the CA and the client and only updated periodically. With OCSP, you get the most up-to-date information on the certificate's status, reducing the risk of relying on a revoked certificate

Answer is CRL. Per Sybex page 27," certificates become invalid for many reasons such as someone leaving the company, information changing or private key being compromised. The CRL signs the list to maintain its accuracy. Page 29: A OCSP has a way to deal with compromised keys when a CRL is used. So we have to assume, there is an OCSP in the environment , and that the CRL list has been configured to select OCS.

OCSP (Online Certificate Status Protocol) is a protocol used to determine the status of a digital certificate, including whether it has been revoked or compromised. When a private key is suspected to have been exposed, the cybersecurity analyst can use OCSP to check the status of the corresponding digital certificate and determine whether it has been compromised. To use OCSP to determine if a private key has been compromised, the analyst can send an OCSP request to the CA (certificate authority) that issued the digital certificate. The CA will check the status of the certificate and return a response indicating whether it is still valid or has been revoked. If the certificate has been revoked, it is likely that the private key has been compromised and should no longer be used

CRL (Certificate Revocation List) is a list of digital certificates that have been revoked by the issuing Certificate Authority before their scheduled expiration date. It is used to verify if a certificate has been compromised and is no longer valid. Answer: B

CRL although it is only good when key is known as compromise

A certificate is irreversibly revoked if, for example, it is discovered that the certificate authority (CA) had improperly issued a certificate, or if a private-key is thought to have been compromised.