ITPEC IP April 2022 Question 43

Digital signature — it lets the recipient verify that the e-mail was not altered after it was signed and that it came from the signer.

The sender computes a hash (message digest) of the message and encrypts it with the sender's private key; the result is the signature. The recipient decrypts the signature with the sender's public key and compares it with a hash computed from the received message. If even one character was changed on the way, the two hashes differ, so the falsification is detected.

Answer (d)

Why not others:

• •(a) IMAP — the protocol for reading and managing mail kept on the mail server; it retrieves messages, it does not check their content
• •(b) SMTP — the protocol for sending and relaying mail; plain SMTP carries no integrity check
• •(c) Information security policy — the organisation's rules and stance on security; a document, not a mechanism that checks a message

Key rule: A digital signature gives integrity (no falsification) and authentication of the sender, but not confidentiality; to keep the content secret, the message must also be encrypted.

Security · AI-written, may contain errors