43. Which of the following mechanism is used to achieve non-repudiation of a message delivery?

Вариант ответа 1 - A. Sender encrypts the message with the recipients public key and signs it with their own private key.

Вариант ответа 2 - B. Sender computes a digest of the message and sends it to a Trusted Third Party (TTP) who signs it and stores it for later reference.

Вариант ответа 3 - C. Sender sends the message to a TTP who signs it together with a time stamp and sends it on to the recipient.

Вариант ответа 4 - D. Sender gets a digitally signed acknowledgment from the recipient containing a copy or digest of the message.