Answer: A digital signature involves encrypting a cryptographic hash, or digest, generated from the message and we will not encrypt the message itself because in general digital signature systems has a feature to be very slow if the message is lengthy so it is better to sign a message which has under gone hash function operation(i.e reduced message) rather than the message itself. Solution Answer: A digital signature involves encrypting a cryptographic hash, or digest, generated from the message and we will not encrypt the message itself because in general digital signature systems has a feature to be very slow if the message is lengthy so it is better to sign a message which has under gone hash function operation(i.e reduced message) rather than the message itself..