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CS Professional · Artificial Intelligence, Data Analytics and Cyber Security - Laws and Practice · Network Basics and Security

A company secretary of a Mumbai firm wants to send a confidential board resolution draft to a director so that only the director can read it. Using public key cryptography, which key should the sender use to encrypt the message?

The sender should encrypt with the director's public key. Only the director holds the matching private key needed to decrypt, so confidentiality is achieved. Encrypting with the sender's private key would only prove origin, because the sender's public key is available to everyone.

  1. AThe sender's own private key
  2. BThe sender's own public key
  3. CThe director's public keyCorrect
  4. DThe director's private key

Explanation

For confidentiality in asymmetric cryptography, the message is encrypted with the recipient's public key so only the recipient's private key can decrypt it. Using the sender's private key would provide authenticity (a signature), not secrecy, since anyone with the sender's public key could read it.

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