Advanced Placement (AP) Computer Science

How does Public Key/Private Key Cryptography ensure data privacy?

1. By allowing anyone to encrypt data.

2. By enabling only the receiver with the Private Key to decrypt the data.

3. By sending messages without encryption.

4. By allowing multiple users to share the same Private Key.

The correct answer is: By enabling only the receiver with the Private Key to decrypt the data.

Public Key/Private Key Cryptography functions on a fundamental principle that ensures data privacy through asymmetric encryption. In this system, each participant has a key pair: a public key that anyone can access and use to encrypt messages, and a private key that is kept secret and known only to the recipient. The critical aspect of maintaining data privacy lies in the private key. When a sender encrypts data using the recipient's public key, only the corresponding private key can decrypt that data. This means that, even if the encrypted message is intercepted during transmission, it cannot be read by anyone who does not have access to the private key. Thus, the recipient is assured that only they can unlock the information intended for them, thereby preventing unauthorized access and ensuring privacy. This mechanism is what makes Public Key Cryptography robust and essential for secure communication, demonstrating a clear relationship between encryption and the exclusive ability of the private key holder to decrypt and access the original data.