Explain the difference between 'public key' and 'private key' in basic cryptography.

• A. A private key is shared to encrypt data; a public key is kept secret to decrypt data.
• B. A public key is shared to encrypt data; a private key is kept secret to decrypt data.
• C. Public key decrypts and private key encrypts.
• D. There is no difference; they are interchangeable.

Answer: (B)

In asymmetric cryptography, you use a pair of keys: a public key and a private key. The public key is meant to be shared openly so anyone can use it to encrypt a message for you. The private key stays secret with you and is used to decrypt those messages. This separation lets others send you confidential data without having to share a secret key in advance. An additional practical point: the same pair can also support digital signatures—signing with the private key and letting others verify with the public key—but for the basic encryption flow, the public key is for encryption and the private key is for decryption.