Discuss classified information over nonsecure telephones is permitted as long as you use which method, if any, of the following?

• A. Encryption
• B. Secure telephone line
• C. None
• D. Physical courier

Answer: (C)

Classified information must be discussed only over approved secure channels. Encrypting a conversation on a standard, nonsecure telephone does not make the channel trustworthy—the entire path, including endpoints and key management, can still be vulnerable to interception or compromise. A truly secure telephone line is designed for classified work, but if you’re on a nonsecure phone, none of the listed methods renders it permissible. The proper rule is to avoid discussing classified material on nonsecure telephones and use only officially approved secure means.