Secure Hash algorithms, such as SHA-1, send encrypted Hash. This Hash can be used to confirm that the data was not tampered with or to confirm the identity of the sender (such as in Digital Signatures). In order to use this Hash as a Digital Signature a. the encryption key used must be generated at both ends of communications independently without transmitting it ever. b. the encryption key must be the private key of the sender. c. only the sender and the receiver should know the encryption key. d. only the administrator should know the encryption key.