Question

A financial controller must send quarterly reports to external auditors by email. Management requires proof that each report genuinely came from the controller and was not altered in transit, and the controller should not be able to later deny sending it. Which cryptographic technique best satisfies these requirements?

Accepted Answer

Applying a digital signature using the controller's private key

Answer

Encrypting the report with a shared symmetric key known to both parties

Answer

Hashing the report and attaching the hash value to the email

Answer

Encrypting the report with the auditors' public key