UESTION 9 Two users want to communicate via email using unsecured channel. The system must ensure the principle of non-repudiation between the two users by signing their certificates. Which of the following should be used to sign their certificates? CSR RA O CRL QUESTION 4 A company requires users to scan their fingerprint to access an application. The developers of the application want to implement multifactor authentication. Which of the following should be implemented? Facial recognition using a camera Have users sign their name naturally Hand geometry scan Implementiris recognition