In public key cryptography, what information must the sender obtain from the recipient before sending data securely?

In public key cryptography, what information must the sender obtain from the recipient before sending data securely?

• A. Computer B's public key
• B. Computer B's private key
• C. A symmetric session key
• D. Computer A's public key

Answer: (A)

Public key cryptography uses a pair of keys: a public key that can be shared openly and a private key that stays secret. To send data securely to someone, you encrypt the data with that person’s public key. Then only the recipient, who has the corresponding private key, can decrypt it. Because of that, you must obtain the recipient’s public key before sending. The private key must never be shared, and while a symmetric session key is often used in practice, it still needs to be securely shared—usually by encrypting it with the recipient’s public key. So the essential information to obtain is Computer B’s public key.

Public key cryptography uses a pair of keys: a public key that can be shared openly and a private key that stays secret. To send data securely to someone, you encrypt the data with that person’s public key. Then only the recipient, who has the corresponding private key, can decrypt it. Because of that, you must obtain the recipient’s public key before sending. The private key must never be shared, and while a symmetric session key is often used in practice, it still needs to be securely shared—usually by encrypting it with the recipient’s public key. So the essential information to obtain is Computer B’s public key.