Which statement describes the process and components of a digital signature?

• A. A password-protected file that encrypts the message.
• B. Hash of message signed with private key; recipient uses public key to verify; components include digest, private key, public key, and certificate.
• C. A symmetric key shared in advance.
• D. A checksum only.

Answer: (B)

Digital signatures authenticate who signed a message and ensure it hasn’t been altered. The process starts by creating a hash (digest) of the message, then signing that digest with the sender’s private key. The resulting digital signature travels with the message, and anyone who has the corresponding public key can verify the signature by re-hashing the received message and checking that the signature matches. If verification succeeds, the recipient gains confidence about the signer's identity and the message’s integrity. The typical components involved are the digest, the private key used to create the signature, the public key used to verify it, and a certificate that ties the public key to the signer’s identity within a trusted framework (PKI). The certificate helps establish that the public key truly belongs to the claimed sender.

Other options describe different concepts that don’t provide a signing and verification mechanism: encrypting a message with a password mainly aims at confidentiality, not authentication; sharing a symmetric key in advance is about secret communication, not non-repudiation or public-key verification; and a checksum is a simple integrity check without any cryptographic proof of origin or identity.