ITPEC FE Morning October 2020 Question 39
ITPEC FE Morning October 2020 — Question 39 of 80
Digital Signature with Private Key — the sender signs with their private key; the recipient verifies with the sender's public key.
How digital signatures work:
- Sender hashes the message and encrypts the hash with their private key → this is the signature
- Recipient decrypts the signature with the sender's public key and compares hashes
- This proves authenticity (who sent it) and integrity (message wasn't altered)
Why not others:
- (a) — describes decryption (restoring encrypted message), not signing
- (c) — describes a fictional scheme with "attached fixed string"
- (d) — describes encryption for confidentiality, not digital signature
Key rule: Digital signature = sender's private key (authentication + integrity). Encryption for confidentiality = recipient's public key.
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