Alice and Bob are good friends and want to exchange messages securely. Alice receives a message from Bob. What key does Alice use to decrypt the encrypted message she received?

Question

Options

• AAlice's public key
• BBob's private key
• CAlice's private key
• DBob's public key

• A
  4% (1)
• B
  8% (2)
• C
  85% (22)
• D
  4% (1)

Explanation

In asymmetric (public-key) cryptography, the sender encrypts a message using the recipient's public key. Because only the corresponding private key can decrypt data encrypted with a public key, Alice must use her own private key to decrypt the message Bob sent her. Bob would have obtained Alice's public key (which is freely shared), encrypted the message with it, and only Alice-the holder of the matching private key-can decrypt it. Using Bob's private key or public key, or Alice's public key, would all fail to decrypt the message.

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