in imSecure 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

the encryption key used must be generated at both ends of communications independently without transmitting it ever.

the encryption key must be the private key of the sender$.$

only the sender and the receiver should know the encryption key.

only the administrator should know the encryption key.