Bob wants to ensure that Alice can check whether his message has been tampered with. He creates a checksum of the message and encrypts it using asymmetric cryptography. What key does Bob use to encryp

Alice's private key is a secret known only to Alice; Bob cannot possess or use it, making this option technically impossible.

Encrypting with Alice's public key provides confidentiality for Alice (only she can decrypt it with her private key), but does not allow Alice to verify that Bob was the sender or that the message was unaltered.

Bob encrypts the checksum with his own private key to create a digital signature. Because only Bob possesses his private key, any recipient (including Alice) can decrypt the checksum using Bob's widely available public key, confirming the message originated from Bob and has not been altered in transit. This mechanism provides both data integrity and non-repudiation.

Encrypting with Bob's own public key means only Bob (with his private key) could decrypt it, which defeats the purpose of allowing Alice or anyone else to verify integrity.