In public-key encryption for confidentiality, can the sender who encrypted the message decrypt it afterwards?

• A. Yes
• B. No
• C. Only if they possess a shared secret
• D. Only if the recipient re-encrypts

Answer: (B)

In public-key encryption for confidentiality, the message is encrypted with the recipient’s public key, and only the recipient’s private key can decrypt it. The sender does not have access to that private key, so they cannot decrypt the message after encryption. If the sender somehow possessed the recipient’s private key, confidentiality would be compromised, but that’s not the normal setup. The other options don’t fit because public-key confidentiality isn’t based on a shared secret, and the recipient doesn’t need to re-encrypt anything for the sender to read it.