An organization uses public key infrastructure (PKI) to provide email security. Which of the following would be the MOST efficient method to determine whether email messages have been modified in…

Sending an encrypted hash (digital signature) alongside the message allows the recipient to re-hash the received message and decrypt the sender's hash using the sender's public key. If the two hash values match, it provides strong assurance of message integrity (not modified) and authenticity (sender verification).

TLS encrypts the communication channel but does not inherently provide end-to-end message integrity for an email once it leaves the TLS tunnel or for messages already compromised before sending.

Encrypting the message with a symmetric algorithm provides confidentiality but does not inherently guarantee message integrity against modification by an attacker who also possesses the key or who modifies it before encryption.

Encrypting the message using the sender's private key provides authenticity (digital signature) but makes the message unreadable by anyone without the sender's public key, which is not typically how email confidentiality is achieved; confidentiality is usually with the recipient's public key.