The public key is used to perform which of the following? (Select THREE).

Question

Options

• AValidate the CRL
• BValidate the identity of an email sender
• CEncrypt messages
• DPerform key recovery
• EDecrypt messages
• FPerform key escrow

• B
  95% (38)
• D
  3% (1)
• F
  3% (1)

Explanation

In asymmetric (public-key) cryptography, the public and private keys are mathematically linked and can each perform operations the other reverses. Three valid uses of the public key are: (B) validating the identity of an email sender - a sender signs a message by encrypting a hash with their private key, and the recipient uses the sender's public key to decrypt and verify that signature, confirming origin; (C) encrypting messages - a sender encrypts a message with the recipient's public key so that only the recipient's private key can decrypt it, ensuring confidentiality; and (E) decrypting messages - when data was encrypted with the corresponding private key (as in signature creation), the public key is the correct key to decrypt/verify it. Key recovery (D) and key escrow (F) are administrative mechanisms involving secure storage of private keys, not public-key operations. Validating a CRL (A) is a PKI trust-chain operation, not a direct use of a user's public key.

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