What is the term for a message digest encrypted with the sender's private key and appended to a message to authenticate the sender and prove message integrity?

What is the term for a message digest encrypted with the sender's private key and appended to a message to authenticate the sender and prove message integrity?

• A. Message digest
• B. Digital signature
• C. Public key
• D. Encryption

Answer: (B)

A digital signature is created by taking a cryptographic hash (message digest) of the message and then encrypting that digest with the sender’s private key. This signed digest is attached to the message. The recipient can verify by decrypting the signature with the sender’s public key to recover the digest and independently hashing the received message. If the two digests match, it proves the message hasn’t been altered (integrity) and that the signer possessed the private key (authenticity/non-repudiation). The plain message digest alone doesn’t provide this authentication, and public key or general encryption terms don’t specifically describe the signing of a digest to prove origin and integrity.

A digital signature is created by taking a cryptographic hash (message digest) of the message and then encrypting that digest with the sender’s private key. This signed digest is attached to the message. The recipient can verify by decrypting the signature with the sender’s public key to recover the digest and independently hashing the received message. If the two digests match, it proves the message hasn’t been altered (integrity) and that the signer possessed the private key (authenticity/non-repudiation). The plain message digest alone doesn’t provide this authentication, and public key or general encryption terms don’t specifically describe the signing of a digest to prove origin and integrity.