CompTIA SecurityX (CAS-005) — Question 19

An internal user can send encrypted emails successfully to all recipients, except one. at an external organization. When the internal user attempts to send encrypted emails to this external recipient, a security error message appears. The issue does not affect unencrypted emails. The external recipient can send encrypted emails to internal users. Which of the following is the most likely cause of the issue?

Answer options

• A. The validity dates of the external recipient’s private key do not match the SSH keys with which the internal user is accessing the system.
• B. The external recipient has an expired public/private key pair that has not been revoked by the CA.
• C. The internal user's company email servers have an incorrect implementation of OCSP and CRL settings.
• D. The external recipient's email address and the email address associated with the external recipient's public key are mismatched.

Correct answer: D

Explanation

The correct answer is D because if the email address associated with the external recipient's public key does not match the email address used by the internal user, the encryption process will fail, leading to a security error. Option A is incorrect as it pertains to SSH keys, which are unrelated to email encryption. Option B is not the issue here since the external recipient can send encrypted emails, indicating their keys are valid. Option C is irrelevant because the problem only occurs with one specific recipient, not all external communications.